A new study demonstrates that programs which work to actively restore rainforests to their former condition are highly successful in helping tropical bird communities recolonise damaged habitat.

Rainforests have long been recognized as incredible hotspots of biodiversity, but large-scale deforestation from the commercial logging industry threatens to level rainforests across the globe. It is no surprise that protecting intact rainforest has long been a goal of conservationists, but at times an already-damaged rainforest comes under conservation policy—and then recovery can present a whole new set of challenges.

In the conservation world, conventional wisdom once held that if an area of wilderness can be protected from human exploitation nature will reassert itself and the damage will be undone over time through natural regrowth. Essentially this philosophy holds that if humans leave nature well enough alone, it will sort itself out.

Undoubtedly this strategy has merit for protecting and conserving our last remaining wildernesses, such as the precious few stands of rainforest that are as yet untouched. But when it comes to the recovery of damaged habitats—which are by far more common than those that are pristine—conservationists and policymakers face important choices. Do they follow a hands-off, passive restoration strategy of leaving nature to nature, or should they engage in active restoration and intervene to speed up the return to a high-quality habitat thriving with the diversity of life?

Yet in order to make these pivotal choices, policymakers need to know if such techniques can actually work to improve the health of impacted habitats. To this end a team of researchers from the Department of Environmental and Biological Sciences at the University of Eastern Finland has undertaken a study to determine if an ongoing active restoration project of a tropical rainforest has been successful, judging by how well the local bird community is able to flourish.

Why look at birds, specifically? In their recently published study the researchers explained that birds are an excellent “indicator taxa” for the overall health of the rainforest, as many bird species have a tendency to be incredibly picky about finding a habitat which has all the right conditions for their survival, and only a truly healthy environment can support a large diversity of species.  Yet a study of this kind—examining whether active restoration of forests can restore bird communities to their pristine state, and how long that takes to achieve—has not really been done before now.

To explore these vital questions the research team journeyed to the Kibale National Park in western Uganda, an area which was once widely decimated by deforestation before conservation organisations and the Ugandan government came together to establish a reforestation plan in 1995. Rapacious plants like elephant grass that suppress tree seedlings were uprooted and replaced with an active tree planting program in the hopes of kick-starting the regrowth of the formerly vibrant rainforest.

For this study the researchers explored six restoration sites throughout Kibale that were enacted over the last couple of decades, from as far back as 1997 to as recently as 2010. They also earmarked three primary forests which were thankfully protected by the National Park before they could be targeted for major exploitation and had never experienced logging or deforestation on a commerialised scale, leaving them virtually undisturbed and an enduring example of what the rest of the park—and indeed, much of equatorial Africa—had once been.

In the autumn of 2013 the eager scientists hiked throughout these study sites for several weeks, diligently recording every bird they heard or saw. At every flash of brightly coloured feathers through the trees, every softly whistled song, the attentive researchers took note. By the end of the study they had identified a grand total of 118 bird species from honeyguides to hornbills, turacos to tinkerbirds.

Snowy-crowned Robin-chats are among the highly specialised species that still struggle to recover. © San Diego Zoo

Snowy-crowned Robin-chats are among the highly specialised species that still struggle to recover. © San Diego Zoo

It didn’t take long for a pattern to emerge. The researchers soon realised that the longer the active restoration had been ongoing, the more similar the bird community was to that which was found in the pristine forests. As the research team moved from young restoration sites to older ones, the highly specialist bird species that require top-quality habitat appeared more and more and the more flexible, generalist species dominated less and less—indicating quite clearly that the active restoration efforts are helping the habitat recover well enough that formerly extirpated rainforest inhabitants are happy to move back in. In fact, based on the pattern of recovery the scientists found, they calculated that active restoration can theoretically return a damaged rainforest to its pre-exploited state in as little as 20 years. Although they acknowledged that in actual practice it would probably take longer than that, the prediction is nonetheless a very encouraging sign.

The implications of the researchers’ findings are a light of hope in the typically somber world of rainforest conservation. Tropical bird communities can and do recover from destruction once exploitation is stopped and restoration is actively assisted. In fact, the scientists point out that the active restoration can jumpstart a positive feedback loop: restored habitat attracts more bird species, which provide ecosystem services themselves through seed dispersal and pest control, that assists in the further recovery of the forest. In addition the results in this study can be used to show that active restoration really does work, which will greatly help any other organisations and governments that are deliberating whether to plan or fund an active restoration project in their own damaged habitats.

Human activity is capable of immense destruction, but this study provides hope that if the same industrial human mind is turned towards vigorous creation instead, the harm we’ve done can be reversed and things can be made right again. Yet this study highlights a word of warning as well: some of the most highly specialised bird species, like honeyguides, were still very rare even in the oldest restoration sites. The authors of the study believe this is likely because there wasn’t enough connection between the scattered oases of quality habitat for the rare birds of these species to truly flourish and that there is still a very real need for protected networks and better connectivity of restored areas.

We are discovering more and more that rather than leaving nature to fix itself on its own, actively working to undo the damage we have done may in fact be much more helpful. While the best way to conserve the incredible biodiversity of rainforest habitat is clearly to prevent largescale human exploitation in the first place, knowing that these places can recover with our aid is nonetheless a great relief.

Reference

Latja, P. et al. (2016) Active restoration facilitates bird community recovery in an Afrotropical rainforest. Biological Conservation 200: 70-79. DOI

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