The resilience of ecosystems

By Thies Loose

The diversity of an ecosystem is closely related to its ability to withstand and adjust in the face of disturbances. This ability is called ecosystem resilience and is a crucial point to consider when thinking about a sustainable future. A more diverse ecosystem will have an easier time adapting to changes in the climate and suboptimal environmental conditions. But what makes an ecosystem resilient?

There are two main drivers at play. The first one is called response diversity, which represents the bandwidth of responses within a functional group to changes in a given environmental driver. If, for example, most green plants in a given ecosystem shared the same narrow temperature range at which they thrive, the primary production would be affected more severely by changing temperatures. A community with plants that have more varied temperature ranges would be more resilient to changing environmental conditions. Besides response diversity, there is functional redundancy. When a species’ population in an ecosystem is fluctuating, the ecosystem functions that species is contributing towards also change. This effect will be less pronounced if there are multiple species fulfilling similar ecosystem functions. Imagine a forest in which a single bird species is responsible for the dispersion of fruiting trees. If this bird’s population was threatened, the ecological dynamics of the system would significantly be impacted. However, with more bird species that fulfil the same function (and are thus “redundant”), the stability of the dispersion of tree seeds would be under less of a threat.

Now, the concept of resilience is pretty straight-forward in “natural” ecosystems, but in cities, things get a little more complicated. The influence of humans changes and convolutes many of the natural processes occurring in urban habitats, and may overshadow natural resilience. Also, there are thresholds of diversity below which resilience does not really “kick in”. This means that small habitats (such as, for example, the biodiversity patches of Campus goes Biodiverse) might be too small for resilience to be applicable. However, this is a matter of scale: For example, while a small urban meadow on its own might not have significant resilience, it still plays a role in the area’s overall resilience when looking at it as part of a network of habitats. This aligns with the goal of Campus goes Biodiverse: Contributing towards a more diverse city, and being part of a network that makes the area as a whole more resilient.