A meta-analysis published today in the journal PLoS ONE (open-access) finds that most disturbed ecosystems are recoverable within a much shorter timespan than previously thought. If people commit to cleanup, restoration or other appropriate management efforts, the researchers say, then most damaged ecosystems can recover in under 60 years – and some in as little as 10 years.
Holly Jones and Oswald Schmitz of Yale conducted the analysis, in which they collected data on ecosystem recovery from 240 studies. Terrestrial ecosystems assessed included old field, grassland, prairie, and scrub habitats, and tropical and boreal forests. Freshwater systems included lakes, streams, and rivers; brackish systems included marshes, wetlands and swamps. Finally, marine systems included coastal, benthic, pelagic and lagoon habitat.
The authors standardized results from the studies by placing variables measured into three broad categories: ecosystem function, animal community or plant community. Ecosystem function variables included nutrient cycling, decomposition rates and abiotic measurements. Animal and plant community variables included estimates of species density, diversity, evenness and species composition.
On average, forest ecosystems recovered in 42 years, while ocean bottoms recovered in less than 10 years. Ecosystems that were affected by many disturbances at once recovered in 56 years, and, surprisingly, those affected by invasive species, mining, oil spills or trawling recovered in as little as five years.
Although these numbers seem surprisingly short, the proportion of studies that found complete recovery of all variables measured was only 35 percent, whereas recovery of some or none of the variables measured was 65 percent.
The authors note that some issues with their results are that some ecosystems might have already been disturbed for awhile before studies on them commenced. Likewise, some studies might have been conducted for too short a time to yield accurate data.
These days, so many ecologists and environmental scientists are resigning themselves to the idea that many ecosystems will never recover to their pre-human state, and focus their energies on making the ecosystem sustainable in its new state instead of restoring its former state. This study comes in direct contradiction to this mindset, suggesting that recovery is not only possible, but could happen quickly. Say the authors:
“Our results are not intended to give license to exploit ecosystems without regard to sustainability. But, with even the best sustainable practices unforeseen outcomes and damages can happen accidentally. The message of our paper is that recovery is possible and can be rapid for many ecosystems, giving much hope for humankind to transition to sustainable management of global ecosystems.”
As ecologists, should we invest in attempting to restore ecosystems that may have undergone a phase shift and may be unrecoverable? Or should we accept new types of ecosystems that haven’t existed before and make sure that they remain sustainable?
Read a Yahoo news story about the article here.
Jones, H., & Schmitz, O. (2009). Rapid Recovery of Damaged Ecosystems PLoS ONE, 4 (5) DOI: 10.1371/journal.pone.0005653