DYVERSE · Vegetation dynamics and ecosystem services provision in a fragmented landscape in response to global change

Vegetation dynamics and ecosystem services provision in a fragmented landscape in response to global change

** Context Human well-being depends on biodiversity and the ecosystem services it provides (such as crop pollination). Global change caused by human activities to satisfy increasing needs in energy and resources, however threatens living diversity, its long-term evolutionary potential and ecosystem functioning. Climate change, habitat loss and habitat fragmentation have been identified as the main threats for terrestrial ecosystems. Habitat fragmentation per se jeopardizes population dynamics and limits their adaptive capacity and migration potential under new climatic conditions, by reducing gene and individual spatial flows. To address these challenges, environmental policies count on land spatial continuities as a central tool for biodiversity and ecosystem services conservation. In this context, land-use change can be seen under two different angles. First, land-use change threatens biodiversity directly through habitat loss and indirectly through their interaction with climate change. Second, land-use change can also be envisioned as the adjustment variable for human adaptation to climate change through land-use planning and the restoration of ecological spatial continuities. In this regards, the main objectives of DYVERSE were twofold. ** Objectives On the one hand, DYVERSE aimed at developing new quantitative tools that are needed to refine our understanding and projections of global change into the coming century. Such tools are necessary to test future scenarios of change and develop the policies and land management strategies (e.g. greenbelts) required to adapt our society to the effects of climate change. On the other hand, DYVERSE aimed at running the previously developed modelling suite in order to assess the joint impact of climate and land-use change on biodiversity and ecosystem services and to develop conservation scenarios accounting for multi-species landscape connectivity. ** Work performed The Monteregie region (southern Quebec, Canada) was taken as a case study for it is both a biodiversity-rich area and a highly fragmented and quickly changing landscape, which shelters and feeds close to 4 million people. Addressing the question of connectivity conservation in a fragmented landscape undergoing climate change, we have developed a multi-species and multi-environmental-change conceptual framework which articulates the different scales involved (local to regional). We have also developed and combined around this framework timely modelling tools incorporating the latest methodological developments. In particular, much work has been dedicated to: 1) the development of a new land-use model able to simulate future potential land-uses by accounting for few simple processes and regional data and some quantitative scenarios on the probable future amount of change; this model makes it possible to test separately the changes in landscape configuration and composition, while conserving a certain stochasticity in the outcomes; 2) the use of graph theory as a basis for landscape connectivity analyses and the definition of climate-proof habitat networks. The use of this theory in spatial ecology is still at its starting ground. Besides these two main achievements, DYVERSE also combined complementary modelling tools such as niche-based models to assess climate-change impacts, hybrid vegetation modeling tool to simulate vegetation dynamics, ecosystem services modelling and habitat quality modelling. For a set of 14 vertebrate species, chosen for their diversity of habitat requirements, life- history traits and dispersal abilities, we have then tested the impact of small-scale land-use change on the overall habitat structure, analyzed the joint effect of climate and land-use change and explored the use of habitat connectivity as a criterion to derive conservation and adaptation strategies. ** Main results Beyond methodological and modelling breakthrough for spatial ecology, DYVERSE also offers a number of innovative basic results. First, we have shown that transfers between scales are not straightforward and that the accumulation of small-scale land-use changes may affect the structure of regional habitat networks non-linearly and with species-specific consequences that are not proportional to the amount of change. In particular, regional patters of land-use change are not similar to random changes and their spatial aggregation makes it possible to orientate the areas to be developed or protected. Second, we have shown that at regional scale climate change are expected to have incomparably larger quantitative effects on habitat networks than land-use change. At regional scale, climatic suitability is indeed rather homogenous and is expected either not to vary (for species close to the center of their climatic niche), to dramatically increase (for species close to the northern boundary of their climatic niche), or to dramatically decrease (for species close to the southern boundary of their climatic niche). Contrastingly, land-use does not have dramatic quantitative effects, but acts via an accumulation effect to modify the local network structure and potentially increase species’ difficulties to migrate across the network under climate change pressure. Third, developing strategies directly accounting for nodes’ importance (nodes betweenness, habitat quality, area) when prioritizing new areas to be dedicated to biodiversity conservation, has turned out to be an efficient way to reduce the negative effects of land-use change in terms of habitat network carrying capacity and traversability. ** Conclusion Through a spatially and temporally dynamic framework, DYVERSE finally provides a new set of modelling tools and timely insights on connectivity conservation that may help addressing the multi-scale land planning challenges our society is facing. Our results on the use of connectivity as a central criteria for reserve selection are encouraging. However, we believe biodiversity and ecosystem services conservation cannot go without a tendency to reduce the amount of habitat loss (e.g. by densifying urban areas) and a direct action to improve landscape matrix’ (around suitable habitat) permeability via the development of appropriate infrastructures (e.g. wildlife ecoduct) and the use of alternative agricultural practices (e.g. agroforestry).

Data: CORDIS, © European Union