functional diversity in avian assemblages in small and large
TRANSCRIPT
Functional Diversity in avian
assemblages in small and large banana plantations in Costa Rica
Anouschka Ahlfert Pearlman
Natural Resource Management,Governance and Globalisation
Master’s Thesis 2007:10
Functional Diversity in avian assemblages in small and large banana plantations in Costa Rica
Anouschka Ahlfert Pearlman
Natural Resource Management, Governance and Globalisation
Master’s Thesis 2007:10
Supervisor: Micke Tedengren, Angelina Bellamy
Centre for Transdisciplinary Environmental Research, CTM Stockholm University
www.ctm.su.se
This thesis is written to fulfil the requirements of the Master’s Programme:
Natural Resource Management, Governance and Globalisation a transdisciplinary programme held by the Centre for Transdisciplinary Environmental Research, CTM, at Stockholm University. The one-year programme consists of four courses and the writing of a Master’s thesis on a subject related to at least one of the courses. 1. Philosophy of Sustainability Science Addresses the difficulties and opportunities in transdisciplinary environmental research. In lectures and seminars participants discuss methodological and epistemological issues such as explanations, causality, systems borders, and objectivity. Held by the Department of Physical Geography and Quaternary Geology Course leaders: Agr.Dr Thomas Hahn and Dr. Miriam Huitric 2. Natural Resource Management and Ecosystem Resilience Focuses on ecosystem capacity to generate life-supporting services, how different management approaches can affect this capacity, as well as which constraints and opportunities are offered by globalisation. Held by the Department of Systems Ecology Course leaders: Prof. Thomas Elmqvist, Dr. Jakob Lundberg and Henrik Ernston 3. Ecosystem Management: Collaboration in Networks and Organisations Investigates the social capacity to develop adaptive governance including arenas for collaboration and conflict resolution. Held by the Centre for Transdisciplinary Environmental Research Course leaders: AgrDr. Thomas Hahn and Dr. Fiona Miller 4. International Governance of Natural Resource Management Uses a macro-perspective on governance. The actors and social-ecological drivers of international regimes are analysed, using case studies that provide a historical and institutional context. Legal as well as normative perspectives are discussed. Held by the Department of Economic History Course leader: Dr. Åsa Vifell More information on the programme is available at http://www.ctm.su.se/egg About The Centre for Transdisciplinary Environmental Research (CTM): CTM aims to catalyse environmental research and promote environmental education across the faculties. CTM is part of Stockholm University and complements the activities of the different academic departments. CTM is also in close cooperation with other Stockholm-based organisations and institutes conducting research in the environmental and sustainable development field. CTM turns science into knowledge by spreading information about natural resources and environmental issues. We also offer seminars and courses on environmental and sustainable development issues. Homepage: http://www.ctm.su.se
Functional diversity in avian assemblages in small and large banana plantations in Costa Rica
Anouschka Pearlman
CTM Department
Stockholm University
May 28, 2007
2 INDEX
SUMMARY page 4
INTRODUCTION page 5
Research Questions page 7
Limitations page 7
THEORETICAL FRAMEWORK & GAPS IN LITERATURE page 9
Adaptive Capacity, Functional and Response Diversity page 10
The role and value of birds page 12
Box A: Birds as Mobile Links page 12
Anthropogenic Habitats page 14
Forest Fragments and Landscape Matrix page 16
Table 1: Properties of land mosaics page 17
Is the Agro-forestry System Better? page 20
Can the Agro-forestry System Address Poverty? page 20
CASE STUDY page 22
Map of Costa Rica page 22
METHODS page 23
Bird Sampling page 23
Habitat Sampling page 24
Bias page 25
FINDINGS page 26
I: Species Diversity page 26
Chart 1: The number of species/birds present per farm page 26
Chart 2: New species recorded per farm page 27
Chart 3: Visual Graph: Accumulative Species page 28
and New Species found
3
INDEX …continued
II: Functional Diversity page 29
Chart 4: Functional Diversity Present page 29
III: Implied Response Diversity page 30
IV: Plant Diversity page 30
V: Habitat Diversity page 30
DISCUSSION
Function and Response Diversity page 32
Plant Complexity and Habitat page 34
CONCLUSION page 35
KEY TERMS page 37
APPENDAGES
Appendage 1: Plant and Bird species per 5m2 page 38
Appendage 2: Species function by diet page 39
REFERENCES page 44
4
SUMMARY
Today there is a growing discourse on how to reconcile preservation and conservation within the
matrix of human-dominated land use systems. This thesis hopes to contribute to new
perspectives on how human landscapes can be managed to co-evolve and co-exist with wildlife
for social prosperity.
By looking at functional diversity present in avian assemblages in 15 small and large-scale
banana plantations in Costa Rica from a systems socio-ecological point of view, this study
determines which farm group (large or small) provided preferred habitat for crucial ecological
processes such as seed dispersal, pollination, pest control and waste management.
Since different species may respond to changes in the ecosystem differently, bird diversity is
analyzed with regards to the functional role that they play and, more importantly, whether there
is redundancy within these roles. Redundancy refers to how many different species of birds are
present in a functional group to respond to current and future system threats.
Management production choices affect plant diversity. Functional diversity in avian assemblages
is compared with plant diversity to see whether there is a positive correlation. A positive
correlation could indicate which types of management choices offer preferred habitat and help
identify characteristics of suitable alternate habitats, networking corridors and steppingstones.
Many of the world’s rural poor rely on land-use for survival, which can conflict with
conservation efforts. Thus, conservation ambitions cannot be undertaken without understanding
and considering the link between land-use and poverty alleviation. Biodiversity can complement
poverty alleviation goals as evidenced by the World Wildlife Foundation Project Report (2006).
Since species’ functions and their habitats can sustain both local and global ecological processes,
they should be the groundwork for any action plan.
5 INTRODUCTION
Managers are increasingly exploring innovative ways to manage for entire assemblages of
species (Meffe et al 2002), but how does one manage for assemblages of species and people,
since it is often argued that the two are opposing goals? Given that many of the world’s rural
poor rely on land-use for survival, it is important to investigate how poverty alleviation and
wildlife preservation can best be addressed with new forms of shared land-use. It is also
important to understand the likely consequences of not managing for assemblages of species and
people since they may be a motivating factor in decision-making processes.
In 2006, the World Wildlife Fund (WWF) released a report entitled “Species and People: Linked
Futures”. In the foreword, Dr. Susan Lieberman writes that modern species conservation
involves conserving and managing a world for both species and people. She argues that “the
dynamics which threaten species are also those which contribute to poverty, such as habitat loss
and its riches, unsustainable depletion of the natural resource base, inequitable access to natural
resources necessary for life, and a lack of appropriate governance and management
mechanisms.” (Lieberman 2006)
This thesis is inspired by the findings of the WWF Report and the challenging linkages
emphasized by Dr. Lieberman-specifically species habitat fragmentation, human land-use
practices and needs, and possible implications for poverty reduction. Dr Lieberman is not alone
in having a holistic view that considers the dynamics between interrelated areas traditionally
viewed as separate policy areas. The literature section of this paper presents other advocates of
this approach, recent literature pertaining to habitat fragmentation, and adaptive capacity theory.
This study takes place in Costa Rica. Agricultural land-use is extremely pertinent to this
geographic area of study. As a developing region, Central America relies on agricultural
production for both local markets and for foreign exchange earnings. Most indigenous groups
practice more traditional forms of agriculture such as shifting cultivation, polycultures or agro-
forestry systems, while other producers may use more intensified methods such as monocultures
involving the use of fertilizers, pesticides and other agrochemicals (Harvey et al 2006). This
study compares the ecosystem health of two farm systems (small and traditional, with large and
production-intensive) using birds as an indicator.
6 Birds are chosen since they can be excellent barometers of environmental health, particularly
when such assessments use summarized data from a wide range of species. (Sutherland et al
2004) Furthermore, the presence or absence of species can reveal important differences between
the habitats/sites. (Ibid) This study therefore:
1) Identifies as many species as possible in order to assess any variation in species diversity
between the small and large farm groups.
2) Places the species into their functional groups based on their diets in order to determine such
variation.
3) Looks within these functional groups for variation in redundancy.
The above is done to determine the adaptive capacity of the small farm group compared to the
large farm group. Functional diversity alone is insufficient to guarantee adaptive capacity. If a
species is unable to continue providing a certain service such as seed dispersal, in the face of
change, another species needs to be present that can provide those services under the new
conditions. The composite of redundancy (or existence of more than one species to fulfill a
functional role in the ecosystem) is what is termed “implied response diversity” in this paper. For
instance, a healthy ecosystem is deemed to be one in which all functional groups have
redundancy thereby contributing to a high level of response diversity. It is implied since
limitations in this study make testing the different species’ responses to change impossible.
However, the field data does make it possible to assess whether redundancy appears to be present
in respective functional groups.
While the farms studied are ecosystems onto themselves, they are also part of a greater
ecosystem—that of the landscape surrounding them. This study also looks for trends in habitat
sites such as surrounding forest fragments.
Plant-bird mutualism is especially dominant in the neotropics. From 50% to over 90% of the
species of tropical shrubs and trees rely on fruit-eating vertebrates to disperse their seeds.
(Fleming et al 1987) Plant diversity in habitats is therefore compared to functional diversity
with the hypothesis of a positive correlation. A positive correlation would suggest that certain
habitats are more suitable for managing ecological processes such as bird functions in
conjunction with agricultural land-use.
The information collected from bird surveys can be used to set conservation priorities, which can
7 hopefully include other small mammals and wildlife. (Sutherland et al 2004)
The aim of this thesis is to contribute to new perspectives reconciling agricultural land-use with
wildlife preservation for mutual prosperity regardless of location, geography and wealth. It also
is part of a PhD project at Stockholm University led by Michael Tedengren and Angelina
Sanderson Bellamy, exploring innovative management practices for sustainable large-scale
agriculture.
RESEARCH QUESTIONS
Using functional diversity (and implied response diversity) as an indicator of adaptive capacity
in small and large banana plantation systems this study asks:
1) Which farm group has the most functional diversity?
2) Does the group with the most functional diversity also have the most implied response
diversity?
3) If there is a difference in amounts of species present between the two farm groups, is there a
possible correlation to plant complexity?
3) Does functional diversity differ between habitat points of interior, edge and forest fragments
in the small and large farm groups?
The null hypothesis is that there is no variation between the farm groups. The assumption is that
the small farm group offers more functional diversity, more implied response diversity, more
plant complexity and more favorable habitat in all three points of interior, edge and forest.
LIMITATIONS
1) Fieldwork data was collected and observations noted during one month only- March 2007.
During that time, plantations visited and birds recorded were limited to availability and
feasibility. Data therefore reflects a snapshot assessment and does not take into account such
cross-temporal aspects as life cycles, breeding periods, and migratory patterns in bird
populations. However, this snapshot view does address spatial scales by looking at small and
large systems.
2) In terms of the small- and large-scale plantations visited, there were disparities in production
8 processes, since the small-scale farms were organic and the large-scale farms were not. This
may affect findings since herbicides are often assumed to diminish habitat conditions. Sites also
differed at regional, altitude and landscape levels; some were near water, national parks,
secondary forests and/or roads. Such variations were noted to account for potential bias.
However, they may also help explain variables favorable for diversity. Since this study focuses
on a comparison of functions present in each farm group as opposed to a comparison of shared
species present, the bias is in itself part of the research question being asked: do large and small
farm systems in various landscape matrix have different avian functions present? The assumption
is that they do, and that this says something about the design of the landscape matrix. While the
importance of the hydrological connection is noted in the literature section, the aquatic findings
by colleagues are not available for consideration at this time.
3) In order to adjust for variations in scale, small farm interiors are compared to point counts in
large farms 30 meters in. In terms of bird recordings the range is set by the audio device used, in
this case a digital voice recorder with a built-in mike. This audio range is small and will not pick
up all species present beyond that range. However, it is a consistent range in all farms recorded,
so there is no bias.
4) Birds were seen in fleeting moments and thus difficult to identify at even genus level. Most
identification became based on audio identification by expert ornithologists. Since the audio
identifications do not clearly show how many birds were present (perhaps 5 were seen and
unidentified and three were recorded by sound) a numerative count is not given. Many species
travel in mixed flocks and the existence of one such species would imply others present although
they may not be caught on tape. To preserve as much integrity as possible, this study counts only
the ones identified with certainty on tape and/or visually and excludes speculation.
5) Response diversity, which is key to assessing adaptive capacity, could not be proven with this
methodology and time frame so it is derived from the functional diversity that the data does
support.
5) Plant diversification is by count but not by species since species diversity is not as important a
variable to birds as is habitat structure. (Sutherland et al 2004) Architectural structure such as
thicket, mid level 2nd forest present, understory and canopy were deemed more pertinent to this
9 study with regards to habitats for birds.
THEORETICAL FRAMEWORK & GAPS IN LITERATURE
This study uses a complex systems view. A complex system is defined more by relationships
than by its constituent parts. Relationships between key entities such as flora and fauna are
largely defined through matter and energy exchanges. (Manson 2001)
The future of biodiversity is dependent on choices in human-dominated landscapes, yet, there is
little scientific basis for assessing the relative biodiversity conservation value of alternate
production regimes and landscape configurations- a basis which is “urgently needed to inform
conservation investments, especially in regions under intensive or rapidly intensifying
production”. (Daily et al 2003) Harvey et al add that relatively few studies have explicitly
compared the biodiversity within traditional indigenous agro-forestry systems to that of more
modern intensified production systems. (Harvey et al 2006) Sinclair and Byrom stress, “renewal
(addition) of habitat is required in order to achieve long-term persistence of biota in functioning
ecosystems. Identification of minimum habitat areas and restoration of ecosystems become two
major priorities for future research. (Sinclair and Byrom 2006) Bennet et al (2004) advocate
functional grouping as a useful starting point to see how species respond to landscape structures
for conservation management.
In order to understand the process of change in ecosystems and ecological functions, indicators
are needed. “Efforts to reduce the risk of undesired shifts between ecosystem states should
develop indicators of ecosystem performance that address the gradual changes”. (Deutsch et al
2003) Developing such indicators to capture shifts in natural capital will become an increasingly
important area for both research and policy. (Ibid)
This study hopes to contribute to those gaps by:
1) Giving a relative biodiversity conservation value on mixed forestry systems and large
intensified systems;
2) Comparing the biodiversity within these systems; and
3) Using functional diversity in avian assemblages and implied response diversity (as a
more precise indicator) for ecosystem health.
10 ADAPTIVE CAPACITY, FUNCTIONAL & RESPONSE DIVERSITY
In this study, adaptive capacity has the following definitions. (For more definitions within these
explanations, please refer to Key Words on page 37).
-Adaptive capacity is the ability of a socio-ecological system to cope with novel situations
without losing options for the future, and resilience is key to enhancing adaptive capacity.
(Folke et al 2002)
-Adaptive capacity in an ecosystem is related to genetic diversity, biological diversity, and the
heterogeneity of landscape mosaics. (Bengtsson et al 2002)
-“Systems with high adaptive capacity are able to reconfigure themselves without significant
declines in crucial functions in relation to primary productivity, hydrological cycles, social
relations and economic prosperity. A consequence of loss of resilience and therefore of adaptive
capacity is loss of opportunity, constrained options during periods of re-organization and
renewal, an ability of the system to do different things. And the effect of this is for the social
ecological system to emerge from such a period along an undesirable trajectory. (Folke et al
2002)
The common denominator in these definitions is that the more options a system has to sustain
itself, the more adaptive it is. Folke et al have said that the diversity of functional groups appear
critical for resilience and the generation of ecoservices (2004) They distinguish two aspects of
such functional diversity: functional-group diversity and functional-response diversity. (Ibid)
Loss of a major functional group cause drastic alterations in ecosystems functions. (Ibid) The
functional groups in avian populations pollinate, spread seeds, control pests, and manage waste.
Elmqvist et al (2003) term variability in responses of species within functional groups as
response diversity. Folke et al (2004) define it as the diversity of responses to environmental
change among the species that contribute to the same eco-function.
For instance, if there are four species offering redundancy of function in one farm’s ecosystem,
that farm will have higher implied response diversity than a farm with only one species offering
redundancy of that function. The first farm will therefore have a higher response diversity
11 capital. With more options in the event of system threats, that farm will therefore also have
more adaptive capacity.
Therefore, response diversity is the main building block to adaptive capacity since
redundancy offers options for response to change. Redundancy refers to the existence of species
in a group capable of carrying out the same function to the same extent. Implied response
diversity means that bird diversity within a functional group offers diversity of responses to
change.
High or low functional and response diversity will reflect high or low adaptive capacity since
response and functional diversity allow the system to reconfigure and maintain crucial functions
in the face of stress or change. (Folke et al 2002) It is not enough to have biodiversity, since that
does not guarantee that species fulfill various functions and are able to respond differently. As
Elmqvist et al (2003) state, the concept of response diversity does not imply that high species
diversity necessarily entails high ecosystem resilience or vice versa, and species rich areas may
be highly vulnerable to environmental change. Thus, while species and functional diversity may
maintain processes in a static setting, it is redundancy that will save these processes by providing
response options when the current state is disturbed or challenged.
When several species perform a similar function, but respond in different ways to environmental
changes in a system, it is resilient. (Folke et al 2002) A system “where functional groups go
extinct or become ecologically insignificant is characterized by low response diversity.”
(Elmqvist et al 2003) Eroding functional and response diversity in a group of seed dispersers, for
instance, diminishes nature’s ability to provide essential eco-services. (Homer-Dixon and Blitt
1998)
High or low adaptive capacity may also give a sense of whether there is a large or small degree
of ecological memory available for landscape and species restoration and/or alternate habitat
building. An ecological process is shaped by its past and the existence of ecological memory in
ecosystems may allow processes to produce ecological pattern that can entrain other ecosystem
variables. (Petersson 2002) The level of ecological memory may or may not correlate to
landscape matrix, or vicinity to primary or second growth, but that cannot be shown in the scope
of this thesis.
12 For the reasons stated above, functional diversity and the implied response diversity are
clearly key to an adaptive system. That is why they are the theoretical framework for this
analysis.
THE ROLE AND VALUE OF BIRDS
Societal development depends on the generation of ecosystem goods and services (Daily and
Ellison 2002). Birds exhibit the most diverse range of ecological functions among vertebrates
with functions ranging from creating soil to shaping primate behavior. (Sekercioglu 2006) Their
most important contribution is as mobile links helping to maintain ecosystem functions, memory
and resilience. Their ecological functions encompass all three major linkages: genetic, resource
and trophic processes. (See box A) Mobile link categories are not mutually exclusive. A species
can modify environments (non trophic) while influencing populations (trophic) and/or dispersing
seeds (genetic) or depositing nutrients (resource).
Box A: Birds as Mobile Links
In terms of pollination alone, roughly two-thirds of the food crops in the world require visits by a
diversity of animal pollinators to set fruit and seed (Folke 2002). In fact, the provision of
dispersal processes is an important reason to minimize species extinctions in communities in
fragmented habitats. (Wethered et Lawes 2005) In tropical forests that have lost their large
mammals, avian seed dispersal may be the only remaining option since birds pollinate dozens of
Functions as Summarized by Sekercioglu 2006
Genetic Linkers: Seed dispersing frugivores and pollinating nectarivores- carry
genetic material from one plant to another or to habitat for regeneration.
Resource Linkers: Piscivorous birds (droppings transport aquatic nutrients to terrestrial
environments)
Trophic Process Linkers: Grazers such as geese and predatory birds such as insectivores and
raptors are trophic process linkers. They influence plant, invertebrate and vertebrate prey
populations.
Non trophic Process Linkers: Ecosystem engineers such as woodpeckers are non tropic process
linkers-they modify their environment by physically transforming materials from one state to
another.
14 crop species and avian seed dispersal is particularly important for big-seeded tropical tree
species such as avocado. (Sekercioglu 2006)
When managing for species function and loss, perhaps redundancy can be a guideline to setting
priorities. For while some species like a keystone have obvious roles, for example bats in Costa
Rica (Elmqvist et al 2003) and the migratory Wildebeest in the Serengeti, (Sinclair and Arcese
1995), others may be less obvious in invaluable roles to an ecosystem, perhaps as a crucial
component to a keystone group. So, if a system reliant on seed dispersers is over-abundant in
trophic linkers but lacking in seed dispersers (who enable plant diversity to sustain populations
and habitats), then perhaps enabling redundancy in seed dispersers becomes the most viable
priority at that point in time to keeping the system adaptive.
15 ANTHROPOGENIC HABITATS
Loss of habitat through clearing for agricultural production is considered to be the major cause of
biodiversity decline around the world. (Major et al 2001) Since many species help shape and
maintain the ecosystems and provide services as per Serkercioglu’s analysis, and since landscapes
and ecosystems determine the health of species populations (Meffe et al 2002), it is crucial to
preserve, and restore their habitats. Human actions are a major structuring factor in the dynamics
of ecological systems. (Folke et al 2002)
Daily et al (2003) argue that biodiversity will depend on how future human food and timber
production is managed in human-dominated countrysides, especially in face of predicted
expansion. Much more understanding is needed on how human-dominated landscapes can
provide alternate habitats and/or restore previous ones, as this may be the future of conservation
management. Co-managing for both wildlife and people is advocated by Dr Lieberman at the
WWF (2006) and echoed by Bengtsson et al (in press). Bengtsson et al point out that while
reserves have long been the cornerstone of biodiversity conservation and contribute to ecosystem
resilience, they need to be complemented with biodiversity management in human dominated
landscapes. (Bengtsson et al in press)
In a recent study done in Nicaragua, shade coffee was shown to provide alternate wildlife habitat
and corridors between forest fragments for howler monkeys and possibly other forest mammals.
(Williams-Guillen et al 2006) High tree diversity ensured year-round availability of food and the
monkeys were able to niche themselves so as not to compete with the frugivore birds. (Ibid) The
study indicated that in terms of species preservation, the future might depend on the ability of
anthropogenic landscapes surrounding protected areas to support basic ecological processes.
(Ibid)
Currently, abandoned cacao plantations are being successfully used as alternate habitats for birds
in the area of Puerto Viejo. (Interview with Daniel Martinez 2007) Daily et al did a study at Las
Cruces and found that coffee and forest remnant sites were very similar to the Las Cruces reserve
in mammalian species richness and abundance. (Daily et al 2003) This shows that restored
habitats can help in conservation however the study does not mention whether the species
composition is the same as that previously lost and whether redundancy had varied since habitat
restoration. Since rustic plantations share many structural attributes normally associated with
forests, including high plant diversity, multi strata structure, constant leaf litter cover, and
16 constant canopy cover which regulates microclimatic conditions in the understory, (Perfecto et
al 1997), it seems likely that they would offer a diversity of habitat options for mammals and
birds that need that architectural complexity.
When managing conservation efforts and adaptive systems, is not enough to consider reserves
and alternate habitats. Powell and Bjork demonstrated that incorporating regional habitat
linkages to allow for seasonal migration of resident species should be a major design criterion for
establishing protected areas since the protected areas are otherwise insufficient without them.
(Powell and Bjork 1994) One of the largest initiatives in the world- the Mesoamerican Biological
Corridor project, which spans 8 countries—hopes to “establish scores of corridors that will one
day connect a rosary of parks and managed lands across Central America to ensure genetic
exchange and habitat preservation in a time when Central American forests are fast disappearing.
“ (Kaiser 2001)
Critics claimed that smaller animals do not avail themselves of corridors; Paul Beier and Reed
Noss proved the contrary. (Ibid) An additional study by Marie Hale showed that changing the
landscape had a large effect on sustaining populations by aiding in genetic dispersal. (Ibid)
Indirect evidence indicates that patches and stepping-stones of preserves and farmlands can help
imperiled bird species as well. (Ibid) Thus, alternate habitats such as abandoned coffee
plantations, corridors, and forest fragments may be helpful components for conservation efforts
in human-dominated landscape designs.
17 LANDSCAPE MATRIX & FOREST FRAGMENTS
Agricultural landscapes are mosaics of different land uses such as horticulture, tree plantations,
grazing pastures, human settlements, roads, streams, and strips and patches of forest and trees-all
elements that can offer an array of habitat for plant and animal species. (Bennett et al 2006)
As Tanner (2006) said in his study in seagrass and mobile epifauna, “The Matrix matters.” He
observed that generalist species (species with a broad niche that can live in many places, eat a
variety of food, and tolerate a wide variety of environmental conditions) appear to be less
influenced by the matrix than are specialist species (Tanner 2006). When it comes to an
agricultural setting, Matlock found that forest fragments support various species depending on
the matrix habitat surrounding these fragments. (Matlock et al 2002)
It has been criticized that the response variable is typically measured only for a particular patch
instead of an aggregate of the entire mosaic. (Bennet et al 2006) The criticism is valid since
reducing the dynamics to one part will not account for the possible properties that emerge when
adopting a systems point of view. In addition, agricultural land mosaics are dynamic and need to
be viewed in temporal scales. (Bennet et al 2006)
This thesis attempts to address the composition and spatial arrangement in relative terms, by
comparing small- and large-scale farms. However, there are no temporal scales addressed, thus
limiting the analysis. (See Table below)
18 Examples of the Properties of individual patches, the landscape context of individual patches, and
emergent properties of “whole” land mosaics, that may affect the status of biota
Individual patches Landscape Context Land Mosaic
Size Adjacent land use Extent of Suitable Habitat
Shape % of habitat in surrounding landscape Composition
Patch type structural connectivity compositional gradients
Core area isolation (distance from) diversity/evenness
Condition -nearest neighbor # of patch types
Disturbance history -conspecific population Configuration
Successional age -similar patch type aggregation
Internal heterogeneity -threatening process number of patches (subdivision)
Structural connectivity
Symmetry
Geographic position
Environmental variation
Range in elevation
Table 1 from Bennett et al, “Properties of land mosaics: Implications for nature conservation in agricultural
environments”, Biological Conservation 133 (2006) 250-264
Changes by man may have subtle effects on the biota over distances much greater than their
components indicate. (Bennet et al 2004) When the structural connectivity of landscape mosaics
and adjacent land-use is disregarded in planning, consequences may be severe. For instance, the
government of Costa Rica has been paying landowners within reserves since 1997 for several
ecosystem services such as carbon sequestration and protection of watersheds, biodiversity, and
scenic beauty. (Daily et al 2000) Despite this, policies are ineffective since they disregard the
interdependence of environmental functions and do not extend beyond reserve borders. (Pringle
2001) In the La Selva–Braulio Carrillo land corridor, deforestation has resulted in runoff with
the undesirable result that local surface and groundwater in certain areas are now contaminated
with sewage, fecal coliformes and other pathogens. (Ibid) Two reserves are located in this
corridor: the La Selva Biological Station and Braulio Carrillo National Park. Pringle warns that
while human disturbances occur outside the borders of these reserves, they may negatively affect
their biological integrity. Therefore, there is an “increasing need for innovative new strategies to
manage hydrologic connectivity across the boundaries of biological reserves as they become
remnant natural areas in human dominated landscapes.” (Ibid)
19
Certainly reserves are important to conservation efforts, however it becomes clear through
Pringle’s study that ecosystems cannot necessarily be contained and managed in a vacuum.
Pringle’s study also highlights the importance of factoring in water availability and usage
patterns with land use and biodiversity preservation. This thesis does not present aquatic data of
colleagues since the findings are not yet available. However, by looking at habitat structure and
avian functional diversity in three points- interior, edge and neighboring forest, a more complete
picture of interconnected dynamics is given than if one were to merely compare an isolated patch
within the interior of each plantation.
Small fragments of natural habitat may be important for birds, in order to maintain their
diversity, resulting in the provision of important services on farms. (Daily et al 2001) When
Daily et al (2001) looked specifically at avifauna in human-dominated landscapes in Costa Rica,
they found a significant positive correlation between forest fragment size and species richness.
Sampling was so different between fragments and open areas however, that they did not compare
abundances therein. (Daily et al 2001)
While Daily compares different sizes of forest fragments, this study looks at whether there is a
difference in avian functions in secondary-growth habitat adjacent to plantations. If there is, this
may indicate that the spatial relations of the farm can determine the efficiency of a forest
fragment.
Matlock et al examined the role of forest fragments in bird habitat and the effect of pesticides on
birds in banana plantations. (2002) The study showed that avian toxicity was high when exposed
to nematicides and chlorpyrifos, but not to fungicides, and it called for more research in this area.
(Matlock et al 2002) According to them, La Selva’s Biological species list constitutes the best
possible pristine standard for comparison with present study results in terms of total species
richness and relative representation of indicator species. (Ibid) Compared to La Selva, 9
frugivores were absent who were also primary forest specialists. (Ibid) This appears to indicate
that the forest fragments were not a successful substitute for species dependent continuous forest.
While moderately sensitive birds were able to use forest fragments associated with agricultural
land, they too faced reductions in population size and range contractions as a result of further
declines in forest habitat. (Ibid) The species that were deemed moderate are not analyzed in
20 terms of functional efficiency so it is hard to assess the ramifications of losing the primary
forest specialists.
This study expects to find moderately sensitive species in the secondary growth adjacent to the
farms visited. It is hypothesized that secondary growth will contain all functions, but that
frugivores may be fewer, especially in secondary growth adjacent to large non-organic farm
systems. This thesis may echo Matlocks findings that forest fragments can play an important role
for moderately vulnerable species and wintering migrants. However, this thesis does not study
avian toxity and uses Matlocks’ findings as secondary information since it was not possible to
gather such field information first-hand within the time period. (Matlock 2002)
While Daily agrees that countryside habitats may sustain a moderate fraction of the native biota,
she cautions that the common occurrence of forest birds in human-dominated countrysides does
not necessarily imply that these species maintain sustainable populations there. About half of the
species have little prospect of surviving outside of the forest, that is they need continuous forest.
(Daily et al 2001)
Wethered and Lawes noted that not all small forest patches are equivalent in the response of bird
species to fragmentation. This is the result of the effect of the matrix type, i.e. different land-uses
in the landscape, on the ability of birds to disperse, which is an important determinant of the size
and composition of bird species assemblages in fragmented landscapes. (Ibid)
When it comes to forest dependent species, the most favorable solution is probably to preserve as
much native forest as possible and maintain current secondary growth. Edward Wilson in the
“Future of Life” advocates keeping “intact the world’s remaining old-growth forests and cease
all logging of such forests” as one of his points in his 8 step program. (Wilson 2002) While
favorable, it may not be the most viable when considering human drivers such as business
interests and land-use needs. A more viable solution when designing agricultural landscapes,
may be to preserve forest in strategic locations and include forest fragments and corridors, which
are large enough to offset negative effects in agricultural areas. Since an additional benefit of
forest fragments is that they provide some watershed protection (Matlock 2002), they can also be
important in terms of protecting water sources for human populations.
21 IS THE AGRO FORESTRY SYSTEM BETTER?
Harvey et al’s study (2006) used terrestrial mammals and dung beetles as indicators for
determining effects of forest fragmentation and habitat destruction in four gradients of land-use
systems from indigenous agro-forestry to intensive monoculture plantains (forests, cocoa agro
forestry systems, banana agro forestry systems and plantain monocultures). They found that
agro-forestry systems have less of a negative impact on at least some components of biodiversity
compared to areas that had been converted to open pastures or crop monocultures, which
dramatically simplifies and modifies the vegetative composition and structure. They also found
that little or no chemicals are more favorable, since they do not contaminate water and adversely
affect animal populations. (Harvey et al 2006) Fieldwork data showed that one species accounted
for 78.9% of all species captured in monocultures whereas two species accounted for 50.31 %
and 51% in the cocoa banana agro forestry systems. (Ibid)
This thesis looks at two systems as opposed to four, and uses birds as an indicator of ecosystem
health. If the findings correlate, this would strengthen Harvey et al’s argument that mixed
systems offer better habitat potential for wildlife and plant diversity. This is especially pertinent
in the neotropics where plant-animal mutualism is most common; 50-90% of the species of
tropical shrubs and trees rely on fruit-eating vertebrates to disperse their seeds. (Fleming et al
1987) Thus, the availability of these trees is important to the continued existence of these
species and vice-versa.
CAN THE AGRO FORESTRY SYSTEM ADRESS POVERTY?
More than 70% of the 1.1 billion poor people surviving on less than one dollar a day live in rural
areas, where they are directly dependent on ecosystem services. Therefore, investing in
environmental assets and management are vital to cost-effective and equitable strategies to
achieve national goals for relief from poverty, hunger and disease. (Peterson SDU brief)
Thrupp (2000) presents the case for agrobiodiversity. About 103 species account for 90 % of the
worlds foodcrops. Rice, wheat and maize account for 60% of the calories and 56 % of the protein
people derive from plants. Reduction in diversity increases vulnerability to climatic and other
stresses, raises risk for individual farmers and can undermine the stability of agriculture. She
concludes that agro-biodiversity yields an array of benefits, contributes to productivity, resilience
22 in farming practices, income generation, nutritional values, food and livlihood security. It also
offers more options to manage crops, lands, water, insects and biota, including habitats and
species outside of the farming systems that benefit agriculture and enhance ecosystem functions.
Perhaps the most compelling recent survey addressing the link between poverty and ecology is
the Millennium Ecosystem Assessment (MEA) that recommends that the world invest in
ecological infrastructure in poor countries and establish a periodic assessment of the benefits that
people obtain from ecosystems. (Sachs and Reid 2005) The MEA’s main accomplishment may
be that it is “a consensus document emphasizing that human-well being depends on healthy
ecosystems” (Stokstad 2005) Healthy ecosystems in this thesis refer to systems that have
redundancy in the bird populations and the habitat structures necessary for their continued
existence and response options while continuing to provide food and income for the farmers.
23 CASE STUDY
Costa Rica has coastlines on the Caribbean Sea and Pacific Ocean. The area studied consisted of
15 farms along the Caribbean slope, specifically small farms in the Talamanca region (near
Puerto Viejo), and large farms in the northern region (Guacimo, Matina, and Siquierres).
Altitude and size varied (from 37 -71 m) between the farms and is a limitation in the study.
Map of Costa Rica
24
METHODS
The methodology for this study was derived from “Bird Ecology and Conservation: A Handbook
of Techniques” by Sutherland, Newton and Green since it is considered an authoritative resource
for the specific task of conducting bird surveys. This study has chosen to assess the species
composition in three sampling points within banana plantations. The sample census (as opposed
to a true census) is taken along a gradient, running from the inside of the farm to the edge of the
farm, and where applicable, into bordering forest area. All of the plantations are located on the
Caribbean coast of Costa Rica.
This method was chosen in order to give a quantitative picture to compare functional diversity
present in large versus small-scale plantation systems. In addition, habitat characterizations
provide data in order to relate bird function, or lack thereof, to a specific habitat. If so, habitat
selection and or preference can be assessed. Such information is important for managerial
choices.
BIRD SAMPLING
Ideally the same researcher collects all of the data to allow for consistency and standardization
(Sutherland et al 2004). That was the case in this study. Bird sampling was done with two to four
point transects along a line from inside the farm to the edge to the outside of the farm. Five
minutes was given to allow the birds to settle. Two five-minute sampling periods were conducted
at each point. Species were recorded as seen or heard and if seen, within a distance of 0-30 or
+30 meters. Local expert ornithologist conducted the post-audio identification since each bird
has numerous calls under different conditions. This was deemed the most reliable way to reduce
identification error.
Most birds were heard and not seen. The audio recordings could not reflect all species present,
but merely those loud enough to be captured within the range of the audio recorder. Out of the
birds seen, some may have been included in the recording; it was difficult to avoid double
counting. A viable solution to maintain integrity is to use only the audio identifications, and the
undisputed visual identifications that were not reflected in the recordings, which reduce the error
25 involved in speculative identifications and miscounts.
HABITAT SAMPLING
The habitat sampling was done as a site characterization. Three 5-meter by 5-meter quadrants
were used. The first located where colleagues placed insect traps, the second 20 meters south and
the third 20 meters east of the second point. There were some modifications such as estimating
20 meters by using 20 paces and going linear in smaller farms along the edge since there was no
other option for an edge. Sticks and rope used to mark these larger quadrants were sometimes
laid on the ground or eyeballed if the vegetation was too dense, mountainous or slippery to
penetrate.
Plant species above waist height, roughly 1 meter were counted and photos were taken of all
species aside from banana and cacao trees which were easily identifiable.
The purpose of the habitat characterization was to gather data for an area comparison. In area
comparisons, one selects areas and relates abundance and presence to habitat. Area comparisons
are more likely to reveal the habitat associations if a wide diversity of sites are used. Biotic
aspects of a bird’s environment can be important influences on distribution, abundance,
reproductive success, and behavior. Thermoregulation is important. Temperature affects birds
indirectly via their food supply. Rainfall, slope, elevation, and soil are additional factors that
have direct or indirect effects on birds. (Ibid) Notes were made of such conditions and adjusted
for when possible.
Detailed recordings of all plant species present in quadrants can provide useful measurements of
vegetation habitats for birds. However, while some plants species are critically important for
nesting or providing fruit, it is usually difficult to relate bird abundance to the abundance of a
long list of species. Habitat structure is usually more important than species composition
according to Sutherland. Therefore the habitat characterization is by structural complexity, not
by species name. The vegetation architecture is equally important since height, structure and
density of vegetation often affects birds by providing perches or cover and by limiting the bird’s
field of view and ability to escape and capture prey. (Ibid)
Line and point transects are the preferred survey methods in many situations since they are
26 highly adaptable, efficient in terms of data collected, and because both can be used to
examine bird-habitat relationships. (Sutherland et al 2004) The standard method is using
quadrants 5m x 5m since larger quadrants have the advantage of reducing the local variation.
BIAS
Both line and point transects for bird counts require a high level of observational skill and
experience since so many contacts and identifications are by call and song only. Few people can
identify everything from brief sight or sound. However, post identification by experts is one way
to ensure that no more than 10% go unidentified. (Ibid) This study consults leading local
ornithologists in order to get as accurate identifications as possible.
In this case, the search area was constrained, making the use of shorter sampling periods for bird
recording. What is most important is that the methods are standardized and replicated at each
site. By standardizing the sampling method and taking numerous samples, the study attempts to
achieve a precise mean for each type of habitat. Precision is determined by two factors: the
sample units visited (number of sites visited and birds counted) and the degree of variation in the
counts made in those sample units. (Sutherland et al 2004)
There is no way to avoid bias. It is there and the list could be extensive. Some birds may make
only one call and if it does not fall into that 5-minute sample count then they are not heard and
counted. Silent and immobile birds are not counted, especially if they are not readily visible
(which most birds are not). Weather conditions such as rain will affect which birds are heard or
seen. Some birds may be scared away, leaving only more tolerant generalist species. As
Sutherland says, “it is an inescapable fact that some birds present will go undetected regardless
of the survey method and how well the survey is carried out.” (Sutherland et al 2004)
By limiting the scope of this study to the recorded species present within the recording range and
the functional diversity these species provide, this study hopes to avoid as much bias as possible.
27 FINDINGS
I: SPECIES DIVERSITY
1) There was no substantial difference in the number of species per farm. 2) Farms 8, 14, and 15
within the larger farm groups, which had different managerial approaches to intensified
production, did not display a difference from the other large farm groups.
Number of species present
Small farms
FARM 1: 13
FARM 2=18
FARM 3=12
FARM 4=7
Large farms
FARM 5=22
FARM 6=10
FARM 7=20
FARM 8= 6
FARM 9=11
FARM 10=20
FARM 11=10
FARM 12=13
FARM 13=11
FARM 14=11
FARM 15=13
Chart 1: The number of species/birds present per farm
True mean of species present small farms 12.50
True mean of species present in large farms 13.00
* Figures are rounded off
28 However, while there was no substantial variation in the total number of species present in the
small and large farm groups, the small farm group has almost 50% more diversity present in
terms of species composition.
The total number of species present in the small farms group as a whole was 33.
The total number of species present in the large farms as a whole was 47.
True mean of bird species per small farm= 8.25
True mean of bird species per large farm= 4.27
In the small farm group, 8.25 out of the 12.5 species counted were unique (that is to say new). In
the large farm group only 4.27 species out of 13.00 were unique. Statistically this shows that the
number of novel species was greater in the small farm group.
Chart 2: New species recorded per farm
# Species # New Sp
Farm 1 13 13
Farm 2 18 15
Farm 3 11 10
Farm 4 6 2
Farm 5 22 22
Farm 6 10 4
Farm 7 20 5
Farm 8 6 0
Farm 9 11 3
Farm 10 20 7
Farm 11 10 2
Farm 12 13 0
Farm 13 11 0
Farm 14 11 1
Farm 15 13 3
29
Chart 3: Visual Graph: Accumulative Species and New Species found
Series 1 represents the total number of species recorded at the farms, and
Series 2 represents the total number of new species recorded at the farms.
30 II: FUNCTIONAL DIVERSITY
The finding that the number of novel species was greater in the small farm group is reflected in
the composition of functional diversity found in the small farm group.
Chart 4: Functional Diversity Present
Total species in functional groups in small and large farms
Number of species which are
Small Farms Large
Farms
Pure frugivores 5 3
Pure insectivores 10 9
Waste management 1 0
Mixed diet 16 34
Omni/small mammals 1 1
*Please refer to Appendage 1 for a breakdown in diet and functions of species
III: IMPLIED RESPONSE DIVERSITY
While the small farm group displays a slightly higher amount of functional diversity, it is not
striking. What is striking is the implied response diversity. The small farms do not have to rely
on as many generalists to perform ecological functions, which specialists have evolved, to do.
By safe guarding their response diversity options, they are therefore better off slightly in quantity
and distinctively in quality of service. Therefore, in terms of the research question, “Does the
group with the most functional diversity also have the most implied response diversity?” the
answer is no. Both groups have functional diversity to a similar extent however the response
diversity is substantially greater in the small farm group. (Bearing in mind that 1) response
diversity here is the ability to continue providing services to the same extent in the face of
changing conditions and challenges, and 2) the large farm groups are substantially larger and
should ideally reflect more diversity and redundancy than the small farm group.)
IV: PLANT DIVERSITY
Plant diversity did not correlate with bird diversity since both the small and large farms
displayed a similar amount of bird species in spite of their differences in vegetation. However,
these differences in vegetation may be a contributing factor for the difference in response
diversity and could be a future research question. (Please refer to Appendage 1)
V: HABITAT DIVERSITY
The interior and edges of monocultures had the same amount of plant complexity except for at
Farm 16 (“Earth 1”) where the edge was right next to a river and secondary growth. Edges were
monotone because usually there was either a canal along the edge, separating the edge from the
other plants; or a hedge and a road that separated the edge from other plant species. This may
explain why so many generalists are present. Thus, while plant complexity does not correlate
with amount of species drawn to the two farm groups, it appears to influence the composition of
specialists and generalists.
32
Chart 5: Plant Species per 5m2 present in the edge and interior of large farms.
Interior Edge
Farm 5 1 1
Farm 6 1 1
Farm 7 1 2
Farm 8 1 1
Farm 9 1 1
Farm 10 1 1
Farm 11 1 1
Farm 12 1 1
Farm 13 1 1
Farm 14 1 1
Farm 15 1 17
DISCUSSION
FUNCTIONS & RESPONSE DIVERSITY
This study set out with the null hypothesis that there would be no variation between the small
and large farm groups. If the findings were to falsify this hypothesis, the questions were 1) which
group had the larger amount of functional diversity, 2) did that group also have the highest level
of (implied) response diversity, 3) did that correlate with plant diversity, and 4), were there
obvious trends between habitat sites of interior, edge and forest? The assumption was that the
smaller agro-forestry systems would be more favorable in all these aspects.
The findings did falsify the hypothesis. By using a simple non-parametric T test for the four
avian functions, where P=0.0625 the hypothesis was falsified by a 93.75% probability with the
assumption that there are differences between the two farm groups being correct. (Personal
Communication Tedengren 2007)
The findings indicated no substantial difference in the amount of species present between the
small and large farm groups when species were given equal weight whether rare, common,
specialist or generalist. The findings differed slightly when species were placed into functional
categories by diet. When looking for redundancy within these functional groups, a substantial
shift from specialists to generalists in the mixed diets sector occured. This seems in keeping
with the nature of fragmented systems; they generally seem to lose specialized species and have
a disproportionately large share of generalist species. (Elmqvist et al 2003) It seems to indicate
that generalists are out-performing specialists since the resources for specialists are dwindling
and, being specialists, they are unable to survive elsewhere.
In biology, generalist species are not the favored option for specialist functions. A generalist
insectivore for instance, will not be as efficient in consuming insects per time unit, as a pure
insectivore will. This is because the generalist will also consume other foods (thereby losing time
it could devote to performing the service of pest control) Given the nature of plant mutualism in
the neotropic, pure forgivers will thus also be more efficient at consuming fruits and dispersing
seeds than generalists. The effects of loss of pollinators have been addressed by Buchman and
Nabhan who showed that even plant species were affected by the loss of pollinators. (Buchman
and Nabham 1997, Folke 2002) This leads to the following speculation: 1) an ecosystem that is
already experiencing a shift to generalists is one that is losing options, the very same options that
help keep a system adaptive. 2) In addition, response diversity, which must be then derived from
34 a generalist pool, cannot be optimal if generalists cannot perform as efficiently as the
specialists whose roles they must assume. 3) If the functions are eventually diluted to a generalist
level, surely the system is low on the quality of response diversity within it. In fact, one could
even perhaps argue that there is no response diversity if the definition requires the ability to
continue to provide services in the same manner. (Even if confidence is placed in generalists
offering redundancy, the generalists may be affected by the loss of specialists due to the
synergistic interactions.)
Specialists have narrow niches. They may be able to live in only one type of habitat, use only a
few types of food, and tolerate a narrow range of climatic and environmental conditions. (Miller
2005) This makes them more prone to extinction when environmental conditions change. (Ibid)
Species reliant on continuous forest are specialists: they cannot survive elsewhere- possibly not
even forest fragments.
Matlock et all (2002) note that insectivore birds that follow army ants are especially vulnerable
to extinction in fragmented habitats. (Matlock et al 2002) Since they lead mixed flocks to the
insects that the army ants flush out, their disappearance would affect other birds following them.
Even common species can be threatened if there is a coevolved association with a vulnerable
species. (Sinclair and Byrom 2006) Conservation needs of one species must take into account the
requirements of other species. (Ibid)
Large frugivores are especially vulnerable to forest fragmentation as well. (Matlock et al 2002)
Since, birds are not equivalent in their ecological roles as seed dispersers (Loiselle and Blake
1999), birds that contribute to quantity dispersal do not necessarily contribute to quality
dispersal. (Ibid) More studies are needed to see whether moderately sensitive frugivore seed
dispersers are capable of providing the same quality as the specialist forest sensitive frugivore
seed dispersers. This will shed light on whether the forest fragments which houses moderately
sensitive species is a solid option for safeguarding functional and response diversity for an
adaptive system.
In addition to the aspect of forest dependency and site sensitivity, there is the aspect of site
fidelity. Warkentin (1995) warned of massive declines in migratory warblers in both Old and
New World Tropics. Two of these three species are highly territorial and insectivores. They may
not be able to adjust to declining rates in prey since they do not flock to find new territories.
35 (Ibid) The effects of this are that they are unable to complete their migratory journey and
provide pest control in other countries, which may lead to an overabundance of pests.
Since there are so many nuances to how functions are performed and prey/food/habitat
preferences for their performance, this study cannot conclude that the implied response diversity
is optimal in the large farm group.
In the small farm group it is likely that it is, since it resembles the original habitat more closely to
begin with. If one considers frugivores alone, three processes: fruit selection, seed handling and
habitat selection directly influence the number of seeds removed and where viable seeds are
deposited in the environment. (Loiselle and Blake 1999) One cannot assume that the presence of
any frugivore will provide optimal dispersion without considering these three processes. The
frugivores in the large farm group, while present, may not be efficient as an optimal response
option. (Optimal refers to an arrangement, which maximizes relevant function.) An optimal
arrangement is necessarily efficient but an efficient arrangement is not necessarily optimal.
(Perman et al 1996)
PLANT COMPLEXITY & HABITAT
While the findings appear to disaffirm that plant complexity correlates with functional diversity,
numerous studies do show that habitat heterogeneity enhances faunal diversity. (Bennet et al
2006) It does appear likely that plant complexity affects species composition since species
diversity is lower in the larger farm groups. Patch level properties, area and structural diversity
were the most important predictors for species richness and avifaunal composition in the study
by Bennet et al. (2004).
In terms of the edge habitat in the large farm group, further studies need to be done to see
whether generalists are out competing edge species and whether this affects response diversity.
Edge species are not restricted to woodland habitat but may nest there while living mainly in
surrounding farmland. (Bennet et al 2004) Hedgerows can serve as additional habitat resource
for some species and can facilitate movement. (Ibid) Since the edge was not present in the
monoculture that may indicate that there is an additional loss of habitat for species that might
otherwise be able to avail themselves of edges and survive there.
36
CONCLUSION
Loss of habitat through clearing for agricultural production is considered to be the major cause of
biodiversity decline around the world. (Major et al 2001) A shift from specialists to generalists
may not be a good sign in a complex system that relies on diversity to weather changes and
specialists that have evolved to provide optimal responses. The large farm group has little
architectural diversity, little or no edge, and fewer specialists. It seems that response options in
this group would have to come from a system already minimal in options if one accepts that
plant complexity, habitat gradients, and a blend of specialists and generalists ready to assume
redundant roles are logical options.
While additional studies need to be done to answer some of the research questions to satisfaction,
the main hypothesis has been falsified by a 93.75% probability that the assumption that there are
differences being correct. While these differences were not as obvious as assumed, it was notable
in the quality of response diversity between the two farm groups.
Species diversity alone does not provide adaptive capacity. If functional diversity does not
include response diversity whether implied or proven, the findings of functional diversity can be
misleading. The question becomes which species are optimal in performing their functions. And
if so, does that optimal functioning decrease when habitat conditions change?
Forest fragments can be habitats for moderately sensitive species. However, the value of
protecting moderately sensitive species should be put in context: is their protection contributing
to species diversity protection or to functional protection or both? If not, fragments should
complement to a greater action plan that does preserve continuous forest in strategic areas for
site sensitive species and migratory birds.
While there is no substitute for true forest, plant architectural and species diversity at the smaller
farmer group indicates that it would be more favorable for other creatures as well. Perhaps large-
scale agriculture can incorporate forest fragments inside the plantations (as opposed to adjacent)
in order to create a canopy and under story more reminiscent of the forest architecture.
37 Erosion of nature’s support system leads to vulnerability. (Folke et al 2002) If part of that
support system is the potential for response under duress, and that response potential becomes
diluted into generalists, then it would seem likely that rural communities dependent on income
from these farms will be vulnerable if the ecosystem fails to continue to provide the services,
which they rely on. Therefore, the low quality in response diversity in the large farm groups can
have exasperate poverty if the eco system and services is weakened in a social-ecosystem that
relies on said services.
In conclusion, the most important realization is that quality and optimal functioning in
redundancy of species should be the focus when evaluating optimal response diversity,
functional diversity and other options that make a system adaptive.
KEY TERMS
The following definitions are taken from “Resilience and Sustainable Development:
Building Adaptive Capacity in a World of Transformations “ by Carl Folke et al. (2002)
Ecological resilience - The amount of change a system can undergo and still remain within the
same state or domain of attraction, is capable of self-organization, and can adapt to changing
conditions
Ecological memory - The network of species, their interactions between each other and the
environment, and the structures that make reorganization after disturbance possible. Its
composition is determined by the past ecological and evolutionary history of the system. The
ecological memory can be divided into the internal memory present within the disturbed area
(also termed 'biological legacies'), and the external memory that provides source areas and
propagules for colonization from outside the disturbed area.
Ecosystem functioning - A summary term for system level processes that are carried out in or
by ecosystems. Some examples are primary production, nutrient cycling, hydrological regulation,
nitrogen fixation, filtration, pedogenesis, maintenance of biodiversity, community (population)
regulation, erosion control.
Functional groups - Groups of species that have similar traits or a similar function in
ecosystems. Examples of functional groups among plants are nitrogen fixers and plants that draw
water from deep in the soil. Other examples are decomposer organisms, mycorhizal fungi, and
predators on pest insects.
Reorganization – re-structuring the biological and social composition of a system and re-
establishing the functioning of the system following disturbance.
Vulnerability - The propensity of social or ecological systems to suffer harm from external
stresses and perturbations. Involves the combination of sensitivity to exposures and adaptive
measures to anticipate and reduce future harm.
Appendage 1: Plant species per 5m2 in relation to Bird Species per habitat
INTERIOR # Plant species per m2 # Bird species recorded
Farm1 1 3
Farm 2 7 7
Farm 3 15 12* inc vulture
Farm 4 21 4* inc vulture
Farm 5 1 5
Farm 6 1 4
Farm 7 1 2
Farm 8 1 2
Farm 9 1 6
Farm 10 1 14
Farm 11 1 8
Farm 12 1 9
Farm 13 1 8
Farm 14 1 6
Farm 15 1 10
EDGE
Farm 1 10 5
Farm 2 8 8
Farm 3 17 N/A
Farm 4 12 Edge same as forest
Farm 5 1 18
Farm 6 1 7
Farm 7 2 12
Farm 8 1 6
Farm 9 1 8
Farm 10 1 12
Farm 11 1 6
Farm 12 1 3
Farm 13 1 6
Farm 14 1 6
Farm 15 17 4
40 FOREST
Farm 1 10* 8
Farm 2 36 8
Farm 3 N/A N/A
Farm 4 N/A 4
Farm 5 16 7
Farm 6 17 N/A
Farm 7 28 10
Farm 8 N/A N/A
Farm 9 N/A N/A
Farm 10 11 N/A
Farm 11 N/A N/A
Farm 12 34 N/A
Farm 13 N/A N/A
Farm 14 N/A
Farm 15 N/A
*The true average in large forests is 21.1. In small forests, it is 23.0.
Appendage 2: Species function by diet
A species that relies on a purist diet is considered a pure frugivores and so forth. A species with a
mixed diet is assumed to also therefore have dual functionality, that is, an insectivore that also
eats seeds upon occasion may act as a seed disperser. However, this would not be its primary
function in the ecosystem.
Diet codes: I= insects
B=berries
S=seeds
M= small mammals
N= nectar
Species at small farms # Farms (f) Sp. large farms
#
Farms (f)
Recorded
at Rec. at
Mealy parrot 1 Frug 0
Red lored parrot 1 Frug 0
White crowned parrot 2 Frug 0
Crimson fronted paraqueet 1 Frug 3
Keel billed toucan 4 Frug 6
Purple throated fruitcrow 1 I, f 0
Cocoa woodcreeper 2 Insect 6
Ruddy woodcreeper 1 Insect 0
Streak headed wood
creeper 1 Insect 0
Bay wren 1 Insect 3
Stripe breasted wren 2 Insect 0
White breasted woodwren 1 Insect 0
42
Boat billed flycatcher 1 I, b, s 2
Bright rumped attila 1 I, b, s 8
Dusky capped flycatcher 1 I, b, s 1
Social flycatcher 1 I, b, s 5
Ochre bellied flycatcher 1 I, b, s 0
Great kiskadee 1 I, f 11
Poultry tyrannies 1 IBM 3
Black faced antthrush 2 Insect 0
Chestnut backed ant bird 3 Insect 2
Western slately antshriek 1 Insect 0
Black cheeked
woodpecker 3 I, b 7
Long billed gnatwren 1 Insect 0
Lesser greenlit 2 I, b 4
Montezuma-o 2 Omni 1
Scarlet rumped casique 1
I, b,
s, n 2
Olive backed euphonia 1 F/s 1
Black striped sparrow 1 B, I 4
Broad winged hawk (mig) 1 I, m 0
Lilaceous trogon 1 F, I 1
Short billed pigeon 1 F, b 0
43 Orange chinned paraq. 5 Frug
Olivaceous flycatcher 4 Insect
Common toddy
flycatcher 5 Insect
Tropical kingbird 4 Dual
Yellow bellied elaenia 2 I, f, s
House wren 10 Insect
Plain wren 2 Insect
Clay colored robin 10 I, f
Great tailed grackle Omni
* Earth Baltimore oriole 4
N, f,
i**
** Fond of nectar
***Locally a pest/
Red throated ant
tanager 2 F/I
Eats sprouting seeds Scarlet rumped tanagers 3 F/b
Of corn or sorghum
****Grass and algae seeds Black headed saltator 3 F, s, I
Buff throated salutatory 8 F, s, n
Grayish salutatory 1 Fib
Blue black gros beak 2 F, s, I
Variable seedeater 7 S, b,
Blue ground dove 5 S, I
Ruddy ground dove 2
Whitetipped dove 1 S, I
Red billed pigeon*** 1 B
44
Groove billed ani 4 I, b
White throated crake 1
I,
s****
Dusky antbird 2 Insect
Barred ant shriek 3 Insect
Hummingbird 1*
Refocus capped
warblers 1 I, b
Grey crowned yellow
throat 4 I, b
Little tinamou 1* S, b, I
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