habitat fragmentation in madagascar: connecting fragmented
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Habitat fragmentation in Madagascar:
connecting fragmented findingsKATHERINE J. KLING1, KIMBERLY YAEGER2, AND PATRICIA C. WRIGHT2-4
1Stony Brook University, Interdepartmental Doctoral Program in Anthropological Sciences (IDPAS), Stony Brook, NY
2Stony Brook University, Department of Anthropology, Stony Brook, NY
3Stony Brook University, Institute for the Conservation of Tropical Environments, Stony Brook, NY
4Centre ValBio, Ranomafana, Madagascar
A systematic review of fragmentation studies in Madagascar, particularly
those examining lemur responses, was conducted with the following
objectives:
1. To quantify trends in the treatment of fragmentation and in the
reporting of responses of lemurs and other Malagasy taxa to
fragmentation
2. To characterize research effort across taxa, study region, and study
type
Systematic Review
― Literature search was conducted in both French and English
December 3, 2018 and April 20, 2019 to identify peer-reviewed
articles presenting research on fragmentation in Madagascar
(PRISMA guidelines for conducting literature review: [11])
― Web of Science, Google Scholar, and targeted journals searched
using search term: “Madagascar fragment*”
― From initial 5,849 records, 1,106 abstracts were reviewed manually
― Sources that did not conduct research exclusively in Madagascar
were excluded
― Further sources excluded that did not explicitly name at least one
study site as a fragment or fragmented forest in either Methods or
Results sections
Data Analyses
― Included sources split between those that statistically tested for
effects of fragmentation on study system (“Tested Articles” (TA) v.
“Untested Articles” (UA)) and for those that specifically conducted
research on lemurs (“Lemur Articles” (LA))
― Trends in included sources analyzed across following categories:- Study type, year published, geographic region, study taxon(a) and IUCN listing,
reporting of fragment metrics, stated test(s) of fragmentation, type of statistically-
tested results reported (positive, negative, not significant)
- Fragment metrics include: area of listed fragment(s), isolation distance from each
other and/or contiguous forest, # of fragments studied
- Primary classifications of tests of fragmentation on study system: by area,
isolation distance, and/or type (comparison of fragment(s) to control sites(s))
- Definition of positive, negative, and non-significant responses of study system to
fragmentation per Carretero-Pinzón [7]
― Data additionally collected regarding authorship and journals in which
studies were published (Fig. 1)
Introduction
Understanding fragmentation’s impact
― The rise in research investigating fragmentation reflects growing
presence of fragmented landscapes themselves [1]
― Biodiversity responses to fragmentation and anthropogenic habitat
change are difficult to categorize, ranging from negative [2] to positive
[2], even for the same species when in different contexts [3]
― Difficulty in defining fragmentation’s impact likely due to confounding
factors associated with fragmentation process (e.g. fragment area,
isolation distance, patch disturbance; [4])
Primates and fragmentation
― Non-human primates are especially susceptible to anthropogenic
landscape change [5]
― Growing research attention [6-7] has assessed primate response to
fragmentation: while no clear trend emerges, species richness tends
to decrease with declining fragment area [8]
Fragmentation in Madagascar
― Madagascar has an extensive and ongoing history of habitat loss and
fragmentation: est. 44% loss of forest cover from 1953-2014 [9]
― As world’s most imperiled vertebrate group [10], summative evaluation
of reported responses of the lemurs of Madagascar to fragmentation
is warranted
Study Objectives
Methods
Results
Summary and Conclusions
Works Cited
Acknowledgements
Literature search
― Search resulted in 67 articles testing impact of fragmentation in Madagascar
(TA), 42 of which focused on lemurs (LA)
― An additional 106 articles reported research within fragments in Madagascar
without explicitly testing the impact of fragmented (UA), 77 of which focused
on lemurs
Study Type, geographic regions, and taxa
― One third of LA presented genetic and biodiversity survey research each and
majority of research (85.7% of LA) concentrated in eastern Madagascar
(Fianarantsoa, Antsiranana, Toamasina, and Toliara provinces; Fig. 2)
― 453 species total were represented across sources, including 46 lemur
species, 80% of which were threatened by extinction (Fig. 3)
― 82.1% of TA included species threatened with extinction in research
― Ten introduced species (e.g. house rat, Rattus rattus, and domestic dog,
Canis familiaris) also covered by research, indicating presence in forest
fragments
Supported by a Graduate Council Fellowship (Graduate School of Stony Brook University) and an
NSF Graduate Research Fellowship (2016203971)
Photo Credits: Nick Garbutt: P. diadema, D. madagascariensis, P. simus; R. A. Mittermeier: I. indri;
Paul Bratescu: E. collaris; Andy Rouse: M. murinus. K. Kling: Fragmented landscape
Figure 2. Map of Madagascar with relative percentage of number of lemur studies (LA) per type
displayed per region. Madagascar and the study sample are divided over each of its six
administrative provinces: 1) Antananarivo Province, 2) Antsiranana Province, 3) Fianarantsoa
Province, 4) Mahajanga Province, 5) Toamasina Province, 6) Toliara Province. Total number of LA
per study type are as follows: Behavior, n = 8; Biodiversity Surveys, n = 14; Genetics: n = 14;
Health: n = 6; Modelling: n = 5; and Other, n = 4. N = 42 LA studies total.
Figure 3. Most-commonly studied lemur species across articles, A) diademed sifaka (Propithecus
diadema; n = 8 studies), B) the collared brown lemur (Eulemur collaris; n = 6 studies), and C) from
top to bottom all n = 4 studies: the grey mouse lemur (Microcebus murinus), greater bamboo lemur
(Prolemur simus), aye-aye (Daubentonia madagascariensis), and indri (Indri indri). Photo credits in
Acknowledgements.
― Fragmentation research in Madagascar covers a wealth of taxa, with
individual studies predominantly focusing on lemurs
― Variable reporting of responses by lemurs to fragmentation results in
difficulty in generalizing its effects
- Wide variety of fragment metrics employed across examined
studies, an unclear distinction between ‘fragment’ and ‘control’
forests, and breadth of tests employed indicates challenge of
working across non-standardized definitions of fragmentation [4]
― The majority of studies report negative responses of Malagasy
biodiversity to fragmentation, yet few study fragmentation per se― Sensu Fahrig [13], fragmentation per se involves testing the impacts of
fragmentation itself, independent of patch size and isolation
― Two studies in this sample examined fragmentation per se via modelling
techniques to determine the relative impact of factors such as patch size, removal,
and isolation [14-15]
― This study emphasizes importance of continued examination of
impact of fragmentation on biodiversity, while encouraging such
research to employ explicit definitions of terms related to
fragmentation and to use comparable testing methods
Kling
Figure 1. All key words that appeared two or more times across TA (n = 59 studies). Key
words are sized according to the number of times they appeared (most frequent:
“fragment*,” 38 times). Note that the stems of words were analyzed to match derivations
of the same concept (e.g. “connect*” could be grouped with “connectivity” or
“connection”).
Defining fragments and fragmentation
― TA conducted research over an average of 8 ± 8.8 fragments each; 5 studies
did not indicate number of fragments studied
― Isolation distances reported (n = 11 studies) ranged from 15-219,000 m
between fragments and/or nearest continuous forest
― Fragment area ranged from 0.16-11,200 ha (five orders of magnitude
difference; median: 57.1 ha; n = 35 studies)
― Control area ranged from 297-104,000 ha (median: 4,143 ha; n = 9 studies)
and did not differ significantly from fragment area (t(12.1) = -2.0, p = 0.07;
Fig. 4)
Tests and impact of fragmentation
― Impact of fragment size most commonly tested (49.3% TA), followed by
studies comparing fragments to one or more control sites (32.8%; note: some
studies applied more than one category of test)
― 23.9% each of TA tested fragmentation by distance and other means (e.g.
consideration of whether land cover types were isolated or connected,
simulated removal of fragments, spatial transformation of landscape across
time)
― For LA, 68.1% of studies reported one or more significantly negative response
of taxa to fragmentation (n = 32 LA; Fig. 5) while only one reported a positive
impact [12]
Figure 4. Area (in hectares) of
study land units by author-
defined type (fragment vs.
control) for total articles (TA)
testing fragmentation by type.
Dark lines indicate means.
Boxes represent standard
error and whiskers standard
deviation. Note all land units,
even replicates used across
studies, are included to
represent what is tested and
reported for overall research
on fragmentation in
Madagascar. N = 187
fragments; 13 control sites. N
= 8 studies (TA).
Figure 3. Number of
lemur-specific sources
(LA) that list the presence
of one or more positive,
not significant, or negative
result as an effect of
fragmentation on study
variables. Sources that
indicated ‘Mixed
responses’ had results of
more than one type
(positive, not significant,
negative). Study that
included ‘Only this
response,’ reported only
responses in one
category. Mixed
responses, n = 17; Only
this response, n = 25.
A
B
C
Figure 6. Fragmented
landscape in southeastern
Madagascar.