by Leta Ames
There is a growing need for climate change models that can accurately represent not only the effects on individual species, but also the interactions and compounding effects within ecosystems. These interactions between species form different “mutualistic networks”. Schleuning et al. (2016) modeled the impact of individual species’ responses to climate change in plant-animal mutualistic networks. Specifically, climatic tolerance of 295 plant species, in eight pollinator networks and five seed-disperser networks in unique areas of central Europe were used to understand the relationship between sensitivity to climate change, climatic niche breadth, and biotic specializations.
Distributional and current range data of plant, insect pollinator, and avian seed-dispersal species in the 13 networks were gridded as 3024 squares (50 by 50 km) and were standardized to a European CGRS grid. Climatic ranges of species were determined using temperature and precipitation data for the gridded areas. Although no relationship was found between plants with larger climatic niches and biotic specialization, animals with larger climatic niches tended to have more plant partners in both types of networks. Similarly, animals that were assumed to be more vulnerable to climate change had fewer unique plant partners. The same pattern was not seen in plants.
To model the effects of climate change on extinctions and coextinctions, Schleuning et. al. built from previous extinctions simulations. The vulnerability to climate change was predicted by comparing current climate suitability to the suitability in two climate change scenarios. The two scenarios were based off projected average increases of 2.85± 0.62℃ and 4.02± 0.80℃, from the Intergovernmental Panel on Climate Change. Extinction was simulated by removing species from the model from highest to lowest vulnerability. Coextinction was modeled by using simulated decreases in the interaction frequencies between partner species. Simulations were created where 25, 50, and 75% decreases in interaction frequency caused an extinction of the partner species. Scenarios with highly specialized partnerships were compared to those with unrestricted partnering of species to account for new partnerships formed as adaptations to climate change.
The simulations demonstrated that animals with more general partnerships were less vulnerable to climate change than specialized animal species. The models also suggest that networks are less able to accommodate loss of plant species than animal species. Plant species’ flexibility to animal extinction can be seen in current communities, such as islands. These models suggest that although animal extinctions may slightly impact individual ecosystems, their widespread impact is minimal. Most importantly, these models predict that climate change will exacerbate the effects of plant extinction on biotic networks due to the “cascading effects” of coextinction. These findings suggest that future climate change models should consider biotic interactions when modeling animal responses.
Schleuning, M., Fründ, J., Schweiger, O., Welk, E., Albrecht, J., Albrecht, M., … & Böhning-Gaese, K. (2016). Ecological networks are more sensitive to plant than to animal extinction under climate change. Nature Communications, 7.