Incorporating the functional dimension of biodiversity throughremote sensing into ecology and conservation

Abstract

Incorporating ecosystem functioning and functional diversity in ecology and nature conservationis key to promote sustainability and a safe operating space for humanity. Nowadays,numerous international agreements, such as the Convention on Biological Diversity (CBD), face the challenge of safeguarding the ecological processes and ecosystem functions that sustain the multiple facets of biodiversity and ecosystem services. Indeed, variables describing ecosystem functioning are widely demanded to define essential biodiversity variables, a framework to coordinate monitoring programmes worldwide. Ecosystem functioning is particularly relevant to track and forecast how environmental changes affect biodiversity and ecosystem services. To characterize ecosystem functioning, multiple remote sensing techniques can be used, such as the Ecosystem Functional Type(EFT) approach. EFTs can be defined as groups of ecosystems with similar dynamics of matter and energy exchanges between the biota and the physical environment. EFTs can bederived from biologically meaningful descriptors (named Ecosystem Functional Attributes -EFAs-) of the seasonal curves of spectral indices as surrogates of focal ecosystem functions, for instance, of primary production dynamics, one of the most essential and integrative indicators of ecosystem functioning.The main objective of this thesis was to provide a remote-sensing based conceptual and methodological approach to incorporate the functional dimension of biodiversity at ecosystem level in ecology and conservation biology through the application of the Ecosystem Functional Type (EFT) concept. We achieved this goal in four steps: 1) First, we provide ground-based empirical evidence for the use of satellite-derived EFTs as descriptors of the regional heterogeneity in ecosystem functioning, i.e., satellite-derived EFTs as homogeneous patches of the land surface in terms of Net Ecosystem Exchange (NEE) dynamics measured onground. 2) Second, we showed how EFTs can be used todescribe the spatial heterogeneity and inter-annual variability of ecosystem functioning (i.e. EFAs and EFTs), ecosystem functional diversity (i.e. EFT richness and EFT rarity) and ecosystem unctional stability (interannual variability and dissimilarity) and released the associated dataset. 3) Third, we provide a proof of concept on how to use EFTs to incorporate ecosystem functional heterogeneity and singularity in setting geographic conservation priorities. 4) Finally, we also provide a proof of concept on how to use EFTs in biological regionalizations to complement the compositional and structural descriptions of biodiversity.Theoretical and empirical models support the relationship between spectralindices derived from satellite images (e.g., Enhanced Vegetation Index -EVI-) and essential functional variables of ecosystems, such as primary production. In this thesis,we identified EFTs from three descriptors of the seasonal curves of MODIS/Terra EVI(MOD13Q1 product): annual mean (proxy of primary production), seasonal coefficient of variation or standard deviation (descriptors of seasonality), and date of maximum EVI(indicator of phenology).Satellite-derived EFTs demonstrated to be an ecosystem functional classification that can inform on homogeneous patches on the land surface in terms of their NEE dynamics measured on ground. Given that NEE dynamics is related toprimary production, a focal ecosystem function, EFTs can then be used (as essentialvariables) to describe, assess and monitor the regional heterogeneity of ecosystem functioning (Chapter I). EFTs also provide a straightforward approach to characterize the spatial diversity,i.e. EFT richness and EFT rarity, and functional stability, i.e. EFT interannual variability and dissimilarity, of ecosystem functioning to inform scientists and managers on ecosystem functional diversity patterns and trends (Chapter II). Furthermore, EFTs helped to both reinforce and complement traditional geographicconservation priorities based on biodiversity composition and structure by incorporating the heterogeneity and singularity of focal ecosystem functions (Chapter III). Finally, EFTs allowed us to understand the relationship between different dimensions of biodiversity in ecological regionalization exercises, i.e. based on biodiversity composition and structure (species distribution, endemisms, vegetation types) and on patterns of ecosystem functioning (Chapter IV). Overall, the characterization of the spatial patterns and temporal variability of ecosystem functioning in terms of EFAs, EFTs, and EFT diversity metrics derived from satellite spectral indices related to a focalecosystem function (e.g. Enhanced Vegetation Index, as a proxy for primary production), demonstrated to be a useful and innovative tool to incorporate ecosystem functioning at regional scale into ecology and conservation under the new conservation paradigm that considers ecological processes and ecosystem functions and services.