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The Combined Effects of Climatic Warming and Habitat Fragmentation on Biodiversity, Community Dynamics and Ecosystem Functioning

Periodic Reporting for period 2 - FRAGCLIM (The Combined Effects of Climatic Warming and Habitat Fragmentation on Biodiversity, Community Dynamics and Ecosystem Functioning)

Reporting period: 2018-12-01 to 2020-05-31

The effects of anthropogenic impacts on biodiversity are varied and complex. Climate change and habitat fragmentation are two of the largest threats to ecosystems globally. To forecast and mitigate their effects is the environmental challenge of our age. Under current policies, future global temperatures will threat up to one out of six species. However, not all species are expected to respond equally. Warming is changing which species are favoured locally, with widespread changes in community composition, biodiversity dynamics, and the functions and services provided by ecosystems. In parallel, habitat fragmentation is a rapidly growing phenomenon that is increasing the isolation of habitat patches. Land use by a growing human population has considerable increased habitat fragmentation for most plant and animal species. This isolation is reducing species persistence and richness, changing species composition, and altering trophic dynamics and nutrient retention and cycling.
Despite substantial progress on the ecological consequences of climatic warming and habitat fragmentation individually, there is a fundamental gap in our understanding and prediction of their combined effects across levels of biological organization. The overarching goal of FRAGCLIM is to determine the individual and combined effects of climatic warming and habitat fragmentation on biodiversity, community dynamics, and ecosystem functioning in complex multitrophic communities. To achieve this, it uses an integrative approach that combines the development of new theory on metacommunities and temperature-dependent food web dynamics in close dialogue with a unique long-term aquatic mesocosm experiment.
FRAGCLIM is articulated around five objectives. In the first three objectives, FRAGCLIM will determine the effects of (i) warming, (ii) fragmentation, and (iii) warming and fragmentation combined, on numerous facets of biodiversity, community structure, food web dynamics, spatial and temporal stability, and key ecosystem functions. Then, it will (iv) investigate the extent of evolutionary thermal adaptation to warming and isolation due to fragmentation, and its consequences for biodiversity dynamics. Finally, it will (v) provide creative solutions to mitigate the combined effects of warming and fragmentation.
FRAGCLIM proposes an ambitious integrative and innovative research programme that will provide a much-needed new perspective on the ecological and evolutionary consequences of warming and fragmentation across levels of biological organization. It will greatly contribute to bridging the gaps between theoretical and empirical ecology, and between ecological and evolutionary responses to global change. Finally, FRAGCLIM will foster links with environmental policy by providing new mitigation measures to climate change in fragmented systems that derive from our theoretical and empirical findings.
FRAGCLIM uses an integrative approach within each of the five work packages that combines development of new theory and experimental manipulations in outdoor mesocosms and laboratory conditions. Also, FRAGCLIM combines ecological and evolutionary responses of biodiversity and ecosystems to climate change and habitat fragmentation. These two conditions (integrative and eco-evolutionary perspective) required establishing a strong and coordinated team to get familiar with the new research areas and methodologies. The multidisciplinary nature of the team, involving ecologists, evolutionary biologists, mathematicians and physicists, required some time for all to understand each other. I believe we have greatly succeeded to do so.
Now, I will detail work performed and main results achieved so far both in the theory developed and the ongoing experiments. We have developed sound and new theory in WP1 (Warming effects) and WP2 (Fragmentation effects). First, we have developed a new consumer-resource model that investigates how stoichiometric constraints affect the response of consumer-resource dynamics to increasing temperature and nutrient inputs (Sentis, Haegeman & Montoya, presentation at the 2018 Gordon Research Conference, and paper recommended in PCI Ecology doi: https://doi.org/10.1101/589895). The main result of this work is that the effects of temperature on food web dynamics, persistence, and biomass distribution across trophic levels largely depend on whether stoichiometric constraints are considered, which is rarely the case. Second, we have shown that habitat fragmentation is key for the stability of food webs, measured by the temporal variability of populations. We developed a new model that reveals that stability increases if habitat loss occurs at random, but stability largely decreases if habitat fragmentation occurs in addition to loss (McWilliams et al. Nature Communications 2019).
In terms of experiments, we were able to set-up and start the long-term aquatic mesocosm experiment, and we are conducting a number of parallel experiments in the new laboratory at my institution. We have had some delays with this from the expected plan, as the mesocosms installation suffered delays out of my control, but such delays do not affect any of the objectives. Experimental results are promising so far, but we are in the process of analysing and interpreting data. Also, given the long-term perspective of our study, this fits with my expectations, as most experimental results will be published in the 4th and 5th year of the grant. For example, within WP1 (Warming), we have found that warming alters biodiversity-ecosystem functioning relationships. At warmer temperatures, biodiversity loss has a larger impact on ecosystem functioning (Bestion et al. Ecology Letters 2019). Also, in WP4 (Evolutionary consequences), we have developed a new framework to understand and predict the eco-evolutionary consequences of warming in fragmented food webs (Faillace, Sentis & Montoya, presentation at the 2018 Gordon Research Conference, and manuscript in review in Biological Reviews).
Finally, we have developed novel methodological approaches that will be of direct application to our experimental data. Of interest for WP2 (Fragmentation) and WP3 (Warming and Fragmentation), we have developed new analysis for disentangling neutral and selective processes in metacommunities (Montoya, plenary at the 2018 Gordon Research Conference, Björk et al. Nature Ecology and Evolution 2019), and to identify modules within complex networks and their relationship with environmental variables, of great relevance for understanding compositional changes in WP 1-4 (Lurgi et al. Nature Communications 2019).
We have already made substantial progress beyond the state of the art, both from a theoretical and experimental perspective.
From a theoretical perspective, we have:
(i) Developed a new individual-based food web model to explore the effects of habitat loss and fragmentation on biodiversity and community dynamics in species-rich multitrophic systems (McWilliams et al. Nature Communications 2019).
(ii) Presented a new consumer-resource theory and model that allows determining how stoichiometric constraints affect the response of consumer-resource dynamics to increasing temperature and nutrient inputs (Sentis, Haegeman & Montoya, presentation at the 2018 Gordon Research Conference, and paper recommended in PCI Ecology doi: https://doi.org/10.1101/589895).
(iii) Developed novel methodologies for biodiversity data, mechanism inference, and structure-function relationships on metacommunities (Björk et al. Nature Ecology and Evolution 2019; Lurgi et al. Nature Communications 2019).
From an experimental perspective, we have:
(iv) Set-up a unique (worldwide) mesocosm experiment to disentangle the combined effects of warming and fragmentation on biodiversity, community dynamics and ecosystem functioning.
(v) Determined how warming alters biodiversity-ecosystem functioning relationships (Bestion et al. Ecology Letters 2019).
I expect numerous results towards the end of the project:
(i) To develop a general predictive theory of the combined effect of warming and fragmentation in ecosystems. To do so, we will continue our development of a temperature dependent-food web model along three directions: (1) Including different temperature-dependence functions, and exploring the sensibilities of different model parameters to temperature changes; (2) Developing a spatially-explicit version of the model to allow fragmentation to happen; (3) Developing an eco-evolutionary version of a simplified version of the model to determine the role and extent of evolutionary thermal adaptation and its feedbacks into community dynamics.
(ii) To test this theory in our outdoors mesocosm experiment, in combination with a series of laboratory experiments under more controlled conditions. In particular, I expect to (1) Establish the temperature dependencies of several biological rates of consumers and resources to better parameterise our models; (2) Determine how warming and fragmentation affect biodiversity, population dynamics and ecosystem functioning across trophic levels and across space; (3) Establish how increases in temperature variability (not only warming) affect biodiversity-ecosystem functioning relationships; (4) Develop a new conceptual framework along with experimental tests for understanding the simultaneous eco-evolutionary consequences of habitat fragmentation and warming for the dynamics of ecological communities.
Also, we will work towards transferring the fundamental knowledge gathered in WP1-4 into applied and restoration ecology, through the organization of a workshop between scientists in the project and politicians, restoration ecologists and ecosystem managers. In addition, we will develop a collaborative programme with the local primary school about warming and fragmentation on aquatic organisms.
Aquatic Metatron for the experiment of climate change and fragmentation