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Biological diversity in an inconstant world: temporal turnover in modified ecosystems

Final Report Summary - BIOTIME (Biological diversity in an inconstant world: temporal turnover in modified ecosystems)

The threats facing ecological communities as a result of climate change, habitat loss, pollution and overharvesting are well known. What is less well appreciated is that ecological communities are constantly experiencing some degree of change due to weather patterns, fluctuations in the abundances of the populations of species that occur there, and through random events. The goal of the BioTIME project has been to understand how this ongoing – and entirely natural – baseline change in natural systems contributes to the maintenance of biological diversity and to what extent it enables these systems to cope with the impacts that result from the human pressure on our planet. BioTIME has addressed this problem in three complementary ways: by using theoretical models to understand how communities work; by analysing data on changes in biological diversity through time; and by applying this knowledge to conservation challenges.

In the first part of the work BioTIME focussed on understanding how ecological communities are structured. We have shown that natural selection operates in different ways on the species that occur in different habitats within a community, and that we can use this knowledge to predict which species will be common. BioTIME has also uncovered evidence that ecological communities are regulated, that is they exhibit a tendency to return to a pre-existing level of richness (number of species) and abundance (number of individuals). However, this regulation does not preclude considerable compositional change.

BioTIME’s second challenge was to quantify baseline change across a range of habitats and taxa, and ask how communities respond when impacted. We tackled this in two ways. 1) An important part of the work was an ‘experiment’ in Trinidad in which we used existing variation in freshwater habitats to understand how aquatic communities change through time. We visited 16 localities in rivers in Trinidad’s Northern Range repeatedly over 5 years, and sampled fish, invertebrates and unicellular organisms. Our data, which consist of >600,000 individual records, show that these taxa respond asynchronously to environmental change. These results raise important questions about the maintenance of ecosystem integrity. 2) We assembled 170 publically available data sets (representing >34,000 species) on ecological communities sampled repeatedly through time, and used these to compare temporal changes in the diversity of a range of organisms (birds, fish, insects, plants etc.) across different regions and ecotypes (land and sea, tropics and temperate zones etc). Our analyses of this BioTIME+ database showed little change in richness but uncovered marked changes in species composition, leading us to conclude that biodiversity change is a more pressing problem than biodiversity loss. A follow-up investigation, which detected pronounced homogenization of groundfish communities in the seas to the west of Scotland linked to climate change, underlined the importance of understanding community compositional change. The BioTIME database is now the largest compilation of ecological assemblage time series data, and will be an important resource for policy makers and ecologists. Our goal is to make all project data fully open access by summer 2017.

BioTIME’s third objective was to apply knowledge gained about temporal changes in biological diversity to real world challenges. An example of one of these is the Mamirauá Reserve in the Brazilian Amazon which is helping protect over 1 million hectares of flooded forest. Our work on the occurrence patterns of rare species in space and time allows us to predict whether a species is rare throughout the region, or just happens to be rare in a locality. This approach allows reserve managers to prioritize species for conservation. We have also shown that careful recreational use does not adversely compromise tropical biodiversity. In addition we have developed new statistical tools for use by policy makers to help protect wild nature.

These three interlinked themes are increasing understanding of how communities change through time, why they change, and the best way of measuring these changes.