The Role of Remote Sensing Data in Conservation and Sustainable Management of the Ecological Functions and Ecosystem Services of Deltas I.J. Harrison a& N. Thomas b

aBelmont Forum Deltas Consortium/Conservation International, Arlington, VA 22202, U.S.A. (E-mail: harrison.deltas@gmail.com )

bEarth Observation and Ecosystems Dynamics Research Lab, Aberystwyth University, Wales, U.K

Deltas are the nexus between land, freshwater and marine systems. They are diverse and functionally complex ecosystems, being extremely dynamic. Some deltas are reducing in size (e.g., through erosion), whilst others are increasing (e.g., through sediment deposition and stabilization by colonization by coastal plants). As a consequence of their biophysical complexity, deltas provide many different ecosystem services – notably fisheries but also coastal protection, water filtration, nutrient cycling and sediment deposition for production of fertile agricultural lands, amongst others. These services have high monetary value compared to many other ecosystems (Fig. 1). Consequently, deltas are economic hotspots, and are home to over half a billion people (Fig. 2), who rely on the services they provide. Deltas are also globally threatened from sea-level rise, river flooding, sediment starvation, agricultural over-use and pollution, hurricanes, and natural and man-made subsidence. The restoration of coastal systems such as deltas is one of the most expensive in comparison with other ecosystems [2]. There is an urgent need for data that can be used to set priorities for the conservation and management of deltas and for measuring how well the targets for management are being met. For example, the Aichi targets of the Convention on Biological Diversity require reporting on the change of ecosystem extent; and sustainable development goals require assessment of the productive function of ecosystems to support human populations. However, direct measurement of ecosystem extent and condition through ground surveys and field sampling can be time-consuming, expensive, or logistically impossible for some regions. Earth Observation technology, which includes remote sensing information, provides a rapid method for obtaining data on the distribution of different habitats within deltas at regional and global scales.

1. Deltas – complex, important, threatened ecosystems

2. Mapping Species Diversity

The evidence above demonstrates the utility of remote sensing data for the conservation and management of deltas. However, 42 years after the adoption of the Ramsar Convention for the conservation and wise use of wetlands, there is not a global initiative for monitoring these systems. In response to this, the DELTAS project, funded by the Belmont Forum, brings together world experts from the physical and social sciences, economics, health/demographics, management and policy, as well as local stakeholders from government, business and non-profit organizations to unify our scientific understanding of deltas as coupled socio-ecological systems. Over the next three years, the cumulative research and knowledge of the team will result in methods to assess delta vulnerability and guide sustainable management and policy decisions at the regional and local scales. The project will include an international repository of integrated data sets (Delta-DAT), a Global Delta Vulnerability Index (Delta-GDVI), and a Delta Risk Assessment and Decision Support Framework (Delta-RADS) for science-based decision-making. The developed Delta-RADS will be an open-source GIS modeling system, allowing for quantitative mapping, definition of functional relationships, and probabilistic modeling of delta processes. The developed concepts and tools will be implemented and tested (Delta-ACT) in three case studies in the Ganges-Brahmaputra-Meghna, Mekong, and Amazon deltas.

Figure 1. Range of values of all ecosystem services provided by different types of habitat (Int.$/ha/year/PPP-corrected). Average value within the range indicated by a star; total number of estimates given in brackets. [1,2]

Figure 3. Global distribution of seagrass species richness [3]

4. Ecosystem function and management – some challenges

Major delta

After CIESIN Columbia Univ (2000)

Scope Principal user requirements where remote sensing/Earth observation data can contribute

Subcomponents of the principal user requiements

Global Global inventory of wetlands

Global extent of wetlands and their temporal variations as an input for global environmental models (carbon, methane production, etc.)

Global monitoring of wetlands with respect to global environmental change

Regional to Local Inventorying and base mapping Wetland boundaries (e.g., size and variation)

Land cover/use of the wetland site and the corresponding catchment area

Digital Elevation Models of the wetland site and the corresponding catchment area

Water regime (e.g., periodicity, extent of flooding)

Water chemistry (e.g., colour, transparency)

Biota (vegetation zones and structure)

Location of potential threats to the wetland

Additional information: e.g., infrastructures

Assessment activities Estimation of biological, physical, and chemical parameter, which characterise the ecological condition of a wetland

Monitoring activities Identification and monitoring of changes in the biological, physical, and chemical condition of the wetland site

Identification and monitoring of threats in the wetland site and the corresponding catchment area, which may affect the wetland condition (e.g., alien species, overgrazing, urban expansion, agricultural activities, industrial pollutants, etc.)

Rapid reaction to catastrophic events (e.g., floods, pollution emergencies)

Implementation of management (e.g., rehabilitation) plans

Base information for inventorying and as a basis for planning and decision-making (e.g., base maps)

Change analysis to monitor the efficiency of the undertaken actions and impact assessment

5. DELTAS project: Catalyzing action towards sustainability of deltaic systems Some ecologically and economically important deltaic habitats can be readily detected and measured in remotely

sensed data. IUCN used LandSat Imagery to define the global distribution of seagrasses as a part of their global assessment of extinction risk for all known species of seagrasses [3] (Fig. 3). Seagrasses act as nursery grounds for many coastal species, and stabilize soft-sediment habitats, protecting coastal zones from erosion and the effects of storms and flooding. Similarly, IUCN used LandSat Imagery to define the distribution of mangroves (Fig 4.) for their assessment of extinction risks and areas of global concern [4]. Mangroves are important nursery grounds for many species that play critical roles in marine, freshwater, and terrestrial food webs and supply people with food. They also supply important coastal protection and have high economic value [5]. Spectral heterogeneity – the spectral variation in remotely sensed signals can be a useful proxy – if used with caution – for species diversity [6]. Several remotely sensed, biological and physical parameters of ecosystems are closely correlated with high levels of species richness and can be used, with caution, to infer biological diversity within an ecosystem [7]. Examples of these are: • Primary productivity • Water temperature • Water flow • Periodicity and extent of flooding

3. Mapping Change Changes in extent of deltaic habitat can be monitored more efficiently through remote sensing rather than through time consuming surveys on the ground. The JAXA Global Mangrove Watch (Aberystwyth University) is assessing changes in the condition of mangrove habitats around the world over a 14 year period. This project has found the rate of change is huge – both in terms of degradation and colonization and is able to locate not only the most threatened mangroves, but provide an insight to the specific pressures put upon them (Fig. 5). This initiative is important in satisfying the need to increasingly quantify the potential impacts of anthropogenic activity upon wetland ecosystems such as deltas, as well as the role of wetland ecosystems in the earth’s global, regional and local carbon and climate cycles. More detailed information on the community structure of wetlands, gained from remotely sensed data can support a better understanding of their production functions. This provides quantitative data so that predictions can be made about the rate at which biomass is produced and carbon is stored. This has important implications for predictions on climate change, species richness and loss and the livelihoods of local populations.

A summary of the diverse ways in which Earth Observation technology can be used for conservation and management of all wetlands, including deltas, is given in Table 1. Our knowledge of ecosystem conditions will result in a better understanding of ecosystem production functions. There are currently gaps in our knowledge that impede progress. For example, we have a basic understanding that deltas are important sites of productivity, but we lack quantitative data that can allow us to describe the rate of production (e.g., hectares or kilos of oyster reef/year). Remotely sensed data can help us make those analyses, and the data allow us to make stronger arguments for supporting conservation and developing markets around conservation. Measurement of changes to deltaic ecosystem size and ecological structure will be particularly important for identifying how their production functions respond to environmental change, particularly climate change. An understanding of the production function of deltaic ecosystems is necessary for describing the full range of essential ecosystem services that deltas provide. While there is a general understanding that ecosystems that are rich in biodiversity have more complex functions and deliver greater services than other ecosystems [8,9], much of this understanding is conceptual and there is an urgent need for more data, to create more extensively tested and meaningful models. More work is needed on the economic values of wetland services – particularly for the ‘non-consumptive’ benefits that are not traded in markets. Nutrient removal, for example, through denitrification is a key service that oyster reefs provide, but is not economically valued and, therefore, not actively managed [10]. Similarly, further information on the contribution that deltas make globally to carbon sequestration will be important for understanding the biophysical effectiveness and economic value that deltas have in adapting to climate change. Remotely sensed data that describe the extent, biophysical characteristics, and compositional turnover of wetlands can help answer these questions on the function and services of deltas, and aid their management, particularly for adaptation to the effects of climate change.

Figure 2. Human population and distribution of major deltas

Table 1. Overview of user information needs and requirements where Earth Observation technology may contribute [11]

REFERENCES 1 de Groot et al. (2012) Global estimates of the value of ecosystems and their services in monetary units. Ecosystem Services 1,50–61 2 Russi et al. (2013) The Economics of Ecosystems and Biodiversity for Water and Wetlands. IEEP London, Brussels 3 Short et al. (2011). Extinction risk assessment of the world’s seagrass species. Biological Conservation 144 , 1961–1971 4 Polidoro et al. (2010) The loss of species: mangrove extinction risk and geographic areas of global concern. PLoS ONE 5(4): e10095. doi:10.1371/journal.pone.0010095 5 Costanza et al. (1997) The value of the world’s ecosystem services and natural capital. Nature 387, 253–260 6 Rocchini et al. (2010). Remotely sensed spectral heterogeneity as a proxy of species diversity: recent advances and open challenges. Ecological Informatics 5, 318–329 7 Kachelreiss et al. (2014) The application of remote sensing for marine protected area management. Ecological Indicators 36, 169–177 8 Cardinale et al. (2012) Biodiversity loss and its impact on humanity. Nature 486, 59-67 9 Hooper et al. (2012) A global synthesis reveals biodiversity loss as a major driver of ecosystem change. Nature 486,105‐108. 10 Piehler & Smyth (2011) Habitat-specific distinctions in estuarine denitrification affect both ecosystem function and services. Ecosphere 2 (1):art12. doi:10.1890/ES10-00082.1 11 Jones et al. (2009) Monitoring and assessment of wetlands using Earth Observation:The GlobWetland project. Journal of Environmental Management 90, 2154–2169 ACKNOWLEDGEMENTS: Many thanks to Mark Spalding (TNC); Mary DeJong (Northern Arizona University); Beth Polidoro, Jan Schipper (Arizona State University); and David Hole, Elizabeth Selig (Conservation International) for information and advice.

Figure 5. Color composite time-series ALOS PALSAR images depicting changes in mangrove forest extent

Figure 4. Global mangrove species richness: native distributions of mangrove species [4]