Rapid recovery of damaged ecosystems

Abstract

Background: Recent reports on the state of the global environment provide evidence that humankind is inflicting great damage to the very ecosystems that support human livelihoods. The reports further predict that ecosystems will take centuries to recover from damages if they recover at all. Accordingly, there is despair that we are passing on a legacy of irreparable damage to future generations which is entirely inconsistent with principles of sustainability.

Methodology/principal findings: We tested the prediction of irreparable harm using a synthesis of recovery times compiled from 240 independent studies reported in the scientific literature. We provide startling evidence that most ecosystems globally can, given human will, recover from very major perturbations on timescales of decades to half-centuries.

Significance/conclusions: Accordingly, we find much hope that humankind can transition to more sustainable use of ecosystems.

Figure 1. Proportion of variables per study that had recovered (white) versus variables that had not recovered (black) separated by ecosystem type (top) and perturbation type (bottom).

We scaled the studies on a per study basis to avoid biasing our results toward ecosystems or perturbation types with higher representation (see text). Proportions are greater than one as a result of single studies having more than one response variable. Higher proportions indicate a higher incidence of recovery (white) or non-recovery (black). We found no significant differences between any of the paired variables, indicating an equal likelihood of recovery or not for all variables. These are conservative estimates of recovery likelihood as we excluded any variables that were headed towards recovery but had not yet fully recovered.

Figure 2. Average recovery times across ecosystems (top) and perturbation type (bottom).

Variables are separated by animal community (black), ecosystem function (white) and plant community (gray) types. Bars represent mean±one standard error.

Figure 3. Geographic locations of the 240 studies used in the synthesis of ecosystem recovery (left).

The number of studies in each ecosystem type (top right) and perturbation type (bottom right). The synthesis shows a high representation of studies across various biomes throughout the globe. Some ecosystem and disturbance types were more highly represented than others in the literature, as indicated by both graphs on the right. Colors represent the spectrum of aquatic to terrestrial ecosystems.

Figure 4. Average recovery times by ecosystem type (top) and perturbation type (bottom).

Forests took longest to recover, whereas aquatic systems required less recovery time than terrestrial systems. Ecosystems took the longest to recover from agriculture, logging, and multiple stressors. Bars represent mean±one standard error. Colors represent the spectrum of aquatic to terrestrial ecosystems.

Figure 5. Relationship between deviation from initial conditions (perturbation magnitude) and the time taken for an ecosystem or community variable to recover.

Data come from a small subset of the 240 studies that measured initial conditions and provided time series data to measure post disturbance levels. The significant relationship depends on the one outlier, indicating more information is needed on perturbations between 500–2000% deviation from initial conditions.