Biodiversity resilience in a tropical rainforest | Nature

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Subjects

- Biodiversity

- Restoration ecology

- Tropical ecology

Abstract

The UN Decade on Ecosystem Restoration aims to stop biodiversity losses1. Approximately 60% of tropical forests have already been lost or severely degraded2, making restoration essential to achieve conservation goals. Recovery trajectories of trees have been studied intensively3,4, but a comprehensive understanding of biodiversity recovery is lacking. Here we analyse recovery trajectories across trophic levels including 16 taxonomic groups from three kingdoms in a lowland tropical forest by investigating resistance to perturbation, recovery times and return rates to old-growth forest conditions. Abundance and diversity regained more than 90% and composition approximately 75% similarity to old-growth forests within 30 years, but full recovery takes several decades. Mobile animal communities acting as seed dispersers or pollinators had high resistance levels and recovered faster than trees or tree seedlings. Return rates contributed 1–2.5 times more than resistance to the recovery times of species composition. Taxon-specific recovery times could not be explained by simple mechanisms (life-history strategies, trophic level or mobility). We show the enormous potential of protecting naturally recovering secondary forests to stop and reverse biodiversity losses.

Main

Tropical forests, harbouring at least 77% of tree species5 and 62% of vertebrate species6 known on Earth, are increasingly under pressure by a combination of anthropogenic stressors, including habitat conversion and degradation, land-use intensification and climate change7,8. Unrestrained deforestation, mainly for conversion to agricultural land9, drives losses in forest area, structure, biodiversity, climate regulation and ecosystem services10,11. Reversing this trend presents an urgent global challenge, mirrored in the United Nations (UN) Decade on Ecosystem Restoration (http://www.decadeonrestoration.org)1. Old-growth forests are irreplaceable11 and need to be conserved. Yet, more than half the tropical forests of the world have already been lost or degraded2. Because 70% of tropical forests are secondary12 (regrowing after deforestation13), their conservation can contribute substantially to achieving global biodiversity conservation goals14,15,16. Tropical forests are dynamic ecosystems in which small-scale disturbance–recovery cycles are an inherent feature of the system13. However, the recovery potential of tropical forest biodiversity in secondary forests is unclear given the large spatial extent and accelerated rate of anthropogenic perturbations in tropical forests around the globe2,13,14,15. Several studies have shown the remarkable potential for natural regeneration of biomass, diversity and species composition of trees across the tropics3,4,17,18,19. The recovery of animal and microbe communities remains poorly studied. Studies indicate that species composition of different animal groups recovers within decades and that animal species richness may recover more rapidly than species composition20,21,22,23. However, these results are mostly based on small samples with few replicates and information across taxa is scattered among different studies, regions and forest types that cannot be compared quantitatively24. Understanding the recovery of several animal taxa alongside trees is essential to allow a holistic and robust estimation of the potential of secondary forests for biodiversity conservation. Improving our understanding of how quickly different taxonomic groups recover could enable more informed decisions about when to use natural regeneration as a cost-effective restoration tool or where assisted restoration measures may be required8,15,19,24,25.

The recovery trajectories and recovery times of ecosystems following a perturbation depend on two components: resistance, defined as the ability to withstand disturbance; and recovery, which is the process of returning to the reference state as measured by the return rate26,27 (Fig. 1). A common definition conceptualizes the combination of resistance and recovery as the resilience of the system4,27,28,29 whereas other works define resilience more narrowly as the speed of return alone30,31,32,33,34. Resistance is related to attributes that confer tolerance to perturbation such as physiological or behavioural plasticity within taxa or features that provide protection against change26,35,36. High return rates are related to low trophic levels37 and to life-history strategies that allow swift recovery after a perturbation, such as rapid recolonization or regrowth26,38,39, rapid reproduction with many offspring, early reproductive age and short generation time40,41,42,43,44. The resistance and return rates of animal taxa that provide key functions, such as flower pollination or seed dispersal, may be essential for successful tropical forest recovery as 90% of the tree species are animal dispersed and 9