The legacy of human disturbance

Human activities partially or totally degrade ecosystems, making them less diverse, less functional and more vulnerable to further change. For years, we have been quantifying the effects of disturbance on ecosystem diversity and function, but less has been known about the effects of disturbance on their recovery. One may think that thanks to the restoration of degraded ecosystems and to increasing ecological engineering and design (e.g., nature based solutions, green infrastructure), we can bring back lost biodiversity and functions, and even justify further degradation.

But, can we actually restore ecosystems? For several years, studies have tried to respond to this question by estimating how much biodiversity and ecosystem functions and services are recovered thanks to restoration efforts. Results have been controversial but it seems that on average ecosystems recover, but three major questions remain unanswered: To what extent? How do we measure ecosystem change? And, how long does it take?

To respond to these questions, we have performed a series of meta-analysis including thousands of ecosystems undergoing recovery from anthropogenic disturbances globally (Figure 1). We have found that recovering ecosystems are less diverse and functional, and host less dense populations than undisturbed ecosystems. We are trying to understand now when they would host similar attributes to undisturbed ecosystems, if they ever do it. These bring up other questions, are restored ecosystems commonly entering alternative stable states? Are these states as resilient as the undisturbed ones? Would they ever reach similar states to those existing in the predisturbance state in terms of stability or resilience?

Figure 1

Meta-analysis and other analytical reviews are extraordinary tools to find patterns of ecosystem recovery, but not to understand mechanisms that may be useful for decision makers, land managers, practitioners, ecological engineers or designers to support their decisions based on hundreds of cases. However, restoration and ecological engineering and design require a deeper insight in the local environment of each particular project, and this is why we also work to understand those mechanisms.