Lost-Biodiv · Predicting changes in species interactions following species loss in hydroelectric reservoir islands

Predicting changes in species interactions following species loss in hydroelectric reservoir islands

Habitat loss, fragmentation and subsequent degradation are primary drivers of biodiversity loss worldwide. In the tropics, hydropower development is a major cause of habitat loss and fragmentation, often creating vast archipelagic landscapes, in which forest islands are isolated within a uniformly hostile open-water matrix. In these archipelagic landscapes, island taxa typically experience a novel hyper-disturbance regime, resulting in drastic shifts in species diversity and community composition through species extinction and turnover. Nevertheless, the burgeoning energy demand worldwide is currently leading to a proliferation of hydroelectric dams across tropical developing countries, which have become the new hydropower frontiers. Here we aimed to demonstrate how pervasive hydropower development has been for biodiversity and ecosystem functioning. With this, we expected to raise European awareness of a problem that affects the entire humanity, and one in which Europe has considerable responsibility as it is one of the main importers of products from developing countries that are directly or indirectly derived from hydropower. With this project we expected to generate knowledge to give foundation to questions such as where to build new dams, whether to create protected areas near hydroelectric reservoirs, and whether to avoid the construction of dams according to the spatial arrangement of the created islands and instead prioritize alternative renewable energy sources. Similarly, policymakers will be able to improve their management policies in widespread European and worldwide fragmented landscapes. NGOs will also take advantage of outcomes of our project, for example, by adopting the methods to be tested in this project, assessing predator-prey interactions to infer on ecosystem functioning, which is simpler than deploying exhaustive census of several taxonomic groups. The initial objective of this Marie-Skłodowska-Curie Action was to dissect the ecological impacts of habitat insularization induced by hydroelectric dams on ecosystem functioning, by comprehensively assessing species interactions across 35 forest islands and three mainland continuous forest sites across one of the largest hydroelectric reservoirs in South America - the Balbina Hydroelectric Reservoir in Central Brazilian Amazon. Firstly, specific prey-predator interactions – herbivory, insectivory and seed predation – would be quantified in situ and related to patch, landscape and habitat-quality metrics. Then, species interactions across terrestrial food webs would be evaluated using theoretical approaches based on species co-occurrence and co-dispersion analysis. Given the impossibility of carrying out any fieldwork during the period of this project (given the COVID-19 pandemic), we have modified the original objectives to: (I) Consider multiple scales and dimensions of diversity to examine the effects of habitat loss and insular fragmentation on lizard and small mammal assemblages (II) Evaluate the effects of habitat loss and insular fragmentation on snake assemblages (III) Examine responses of a major herbivore, the leaf-cutter ants, to habitat loss and fragmentation, and their inter-trophic relationships (IV) Apply species-habitat networks to investigate the effects of habitat loss and insular fragmentation on eight major biological groups Overall, we conclude that hydropower development, by creating small, habitat-degraded islands that harbour reduced taxonomic, functional and phylogenetic diversity of species, has major detrimental effects on biodiversity. To preserve the multiple dimensions of species diversity, thereby maintaining the health of the ecosystem, setting-aside large forest tracks should be imperative.

Data: CORDIS, © European Union