New Frameworks Needed to Balance Costs and Ecological Benefits of Active and Passive Forest Restoration
Brancalion, P., D. Schweizer, U. Gaudare, J. Mangueira, F. Lamonato, F. Farah, A. Nave, and R. Rodrigues. 2016. Balancing economic costs and ecological outcomes of passive and active restoration in agricultural landscapes: the case of Brazil. Biotropica 48:856-867.
To plant or not to plant? This is one of the most common questions that restoration practitioners face when deciding how to restore a native ecosystem. Planting seedlings can speed up ecosystem development and reintroduce species of interest, but may also lead to high implementation and maintenance costs. A consequence of these trade-offs is that restoration practitioners have to make hard choices between investing more money per unit of area to obtain a higher quality restoration or using the same amount of money to restore a larger area with lower quality restoration. In addition to ecological efficiency and costs, there may be legal constraints to the use of natural regeneration, as compliance with legal instruments may require that restoration projects achieve mandatory minimum ecological standards within a few years.
To address the critical challenge of improving the knowledge basis to support the selection of restoration approaches, we assessed the factors driving the proportion of land allocated to passive and active restoration in 42 programs covering 698,398 hectares of farms in the Atlantic Forest, Atlantic Forest/cerrado ecotone and Amazon. We also assessed the ecological outcomes of passive and active restoration in 2955 monitoring plots placed in six restoration programs and the legal framework developed by some Brazilian states to balance the different restoration approaches and comply with legal commitments. As expected, active restoration was the most commonly used restoration approach, as most of the restoration programs surveyed were implemented to comply with the Forest Code. The restoration sites established through tree plantations showed a slightly better performance for some ecological indicators. Surprisingly, the ecological outcomes of tree plantations were as variable as those of passive restoration, overturning the rule that tree plantations result are a more predictable approach.
Large-scale restoration relies on promoting passive restoration. The use of this approach may rely on the modification of existing legal instruments in order to better deal with its inherent uncertainty. For instance, new legal frameworks in Brazil have considered land abandonment for up to four years before deciding on a restoration approach, to favor the use of passive restoration. The way forward requires a better understanding of the drivers and triggers or natural regeneration, the development of predictive models that inform the areas with higher chances of natural regeneration, and the establishment of legal instruments that are more realistic in terms of what can be achieved by restoration in a given timeframe.
The PARTNERS connection
This paper was published in a special issue of Biotropica that was organized by PARTNERS, with the aim of compiling a collection of high-level publications about the main challenges for large-scale restoration. This special issue was an important incentive for this paper, and the discussions authors had with other PARTNERS members during the workshops were essential for consolidating the idea of this work and presenting this case study from Brazil for an international audience.