Poorly designed tree planting campaigns could do more harm than good


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Campaigns to plant large numbers of trees could backfire, according to a new study that is the first to rigorously analyze the potential effects of subsidies in such programs.

The analysis, published on June 22 in Sustainability of nature, reveals how efforts like the Global Trillion Trees Campaign and a related initiative (HR 5859) under consideration by the US Congress could result in increased biodiversity loss and little, if at all, climate change. The researchers point out, however, that these efforts could have significant benefits if they include strong subsidy restrictions, such as a ban on replacing native forests with tree plantations.

“If policies to encourage tree plantations are poorly designed or poorly implemented, there is a high risk of not only wasting public money, but also of releasing more carbon and losing biodiversity,” he said. said study co-author Eric Lambin, Professor George and Setsuko Ishiyama Provostial. at the Stanford School of Earth, Energy and Environmental Sciences. “This is exactly the opposite of what these policies are aimed at.”

There is no doubt that forests have a disproportionate role to play in efforts to slow the loss of global biodiversity and tackle climate change by sequestering carbon in the form of biomass. So it makes sense that tree planting as a solution has gained traction in recent years with ambitious commitments, such as the Bonn Challenge, which aims to restore an area of ​​forest more than eight times the size of California’s. ‘by 2030, and Trillion Trees, which is looking to plant as many trees as the name suggests.

A closer look reveals flaws in the optimistic plans. For example, nearly 80 percent of Bonn Challenge commitments involve planting monoculture tree plantations or a limited mix of trees that produce products such as fruits and rubber rather than restoring natural forests. Plantations generally have much less potential for carbon sequestration, habitat creation and erosion control than natural forests. The potential benefit diminishes further if the trees planted replace natural forests, grasslands or savannas – ecosystems that have evolved to support unique local biodiversity.

In the new study, researchers critically examined another aspect of some mass tree planting efforts: grants designed to encourage private landowners to plant trees. Such payments are widely offered as a promising solution to a variety of environmental challenges. Thus, scientists looked at one of the oldest and most influential afforestation subsidy policies in the world, Chile’s Legislative Decree 701. The law, in effect from 1974 to 2012 and currently being considered for reintroduction, has served as a model for similar policies in a number of South American countries and international development projects.

“In light of the global enthusiasm for planting a trillion trees, it is important to reflect on the impact of past policies,” said lead author Robert Heilmayr, assistant professor at UCSB, who worked on the study while a doctoral student in the interdisciplinary Emmett program. in Environment and Resources at Stanford School of Earth, Energy and Environmental Sciences. “Chile’s experience can help us understand the climatic, ecological and economic impacts that could arise when governments pay landowners to establish massive tree plantations.”

Chile’s Legislative Decree No. 701 subsidized 75 percent of afforestation costs and provided support for the continued management of the plantations. Lax enforcement and budget restrictions have hampered bans on the use of subsidies on land already forested, leading to situations in which the government has subsidized the replacement of native forests with profitable tree plantations. Anecdotal evidence indicated that the law subsidies further reduced native forest cover by encouraging the establishment of plantations on shrub areas or marginal agricultural land where forests might have regenerated naturally.

The researchers set out to quantify the total impact of afforestation subsidies and calculate their effects on net changes in carbon and biodiversity across the country. They compared the area of ​​Chilean forests under three scenarios: the actual subsidy patterns observed, no subsidy, and subsidies combined with fully enforced restrictions on the conversion of native forests to plantations. They found that, compared to a no-subsidy scenario, reforestation payments increased the area covered by trees, but decreased the area of ​​native forests. Since Chile’s native forests are more carbon dense and rich in biodiversity than plantations, the subsidies have failed to increase carbon storage and have accelerated biodiversity losses.

“Nations should design and implement their forest subsidy policies to avoid unwanted ecological impacts resulting from the Chilean program,” said study co-author Cristian Echeverría, professor at the University of Concepción in Chile. “Future grants should seek to promote the recovery of the many natural ecosystems rich in carbon and biodiversity that have been lost.”

Source of the story:

Materials provided by Stanford University. Original written by Rob Jordan. Note: Content can be changed for style and length.

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