Systemic Conservation Biology addresses questions how natural ecosystems respond to anthropogenic stressors and disturbances. Centrally important examples of these anthropogenic stressors include global warming, nutrient enrichment, and habitat destruction. In contrast to traditional Conservation Biology, the focus of Systemic Conservation Biology is on entire systems comprising multiple populations, their abiotic environment and system-level functions.
The scientific approach of the Systemic Conservation Biology Group is based on describing the Ecological networks composed of populations (the network nodes) and their interactions (the network links or edges). Trophic interactions (e.g., predator-prey, parasite-host, parasitoid-host, herbivore-plant) are the life-sustaining, energetic backbone structure of any natural ecosystem, and they compose complex food webs (see figure below for an example). Any heterotrophic population will need these food-providing links to balance its metabolic energy expenses and maintain its life. Autotrophic populations such as most plants derive energy from abiotic resources and support the entire energy requirement of the food web at its base. In addition to the trophic energy fluxes, ecological networks also include non-trophic interactions such as competition and facilitation. Although these interactions do not directly provide food for the populations, they can be of crucial importance in modifying these energy fluxes, the population densities and their traits.
Classic Theoretical Network Analyses predicted that complex ecological networks are unstable and unlikely to persist. Additionally, this instability increased with the species richness (diversity) and the connectance (complexity, expressed as the probability that any pair or species is linked by an interaction) of the networks. This chronic instability of the complex networks should theoretically lead to severe waves of species extinctions that eventually deconstruct diverse and complex networks into simple communities of few species. This theoretical perception of complex ecological networks is in sharp contrast to the high diversity and complexity of stable natural ecosystems. Moreover, the instability of complex network models has hindered the model development how natural communities respond to external stressors. For several decades, one of the most central challenges in biological network sciences has thus been to understand the “devious” strategies employed by natural food webs to overcome this chronic instability. Several seminal studies have demonstrated that natural food webs posses non-random structures of their links (who is consuming whom) and interaction strengths (i.e., strength of energy fluxes through the links). This non-randomness of the food webs provides the critically important network stability by constraining the universe of possible network configurations to those that are intrinsically stable.
The Systemic Conservation Biology Group employs an approach that adds the body-size structure of natural food webs to the network analyses. As the population-averaged body masses determine most biological rates such as the respiration and feeding rates, they are of central importance for the network structures and energy fluxes. Theoretical work in the Systemic Conservation Biology Group demonstrated that implementing natural body-size structures in models of complex food webs yields stable networks. In addition to reconciling lingering gaps between empiricists (working in stable complex networks) and theoreticians (addressing questions in arbitrarily simple models), this new approach allows targeting applied questions in a realistically complex model environment.
Projects in the Systemic Conservation Biology Group include:
the body-size structure of natural food webs;
effects of body sizes on biological rates and interaction strengths (functional responses);
predicting the consequences of species loss in complex networks;
understanding the effects of global warming and nutrient enrichment on complex networks.
A more detailed description of the projects can be found in the Research section.