Tree planting is not a simple science, Holl & Brancalion 2020

Well-planned tree-planting projects are an important component of global efforts to improve ecological and human well-being. But tree planting becomes problematic when it is promoted as a simple, silver bullet solution and overshadows other actions that have greater potential for addressing the drivers of specific environmental problems, such as taking bold and rapid steps to reduce deforestation and greenhouse gas emissions [Holl 2020: 580].

Some of the pitfalls to avoid in tree planting initiatives, according to the authors, include:

• Use of non-native species, which does not result in a true forest and can result in ground water depletion in arid environments.
• Planting trees in historic grasslands and savannas, harming those native ecosystems and species.
• Abandoning trees after they are planted, which can result in high mortality due to insufficient water for developing saplings, being shaded out by faster growing herbaceous plants, grazing, or being re-cleared.
• Planting trees in agricultural land, which risks pushing crop production into native forest land, which is then deforested.

The authors insist that reforestation takes careful planning, stakeholder engagement, clear goal-setting, and long-term monitoring and adaptive management of planted tree stands to ensure their survival. Above all, existing mature, native forests should be preserved.

The first priority to increase the overall number of trees on the planet must be to reduce the current rapid rate of forest clearing and degradation in many areas of the world. The immediate response of the G7 nations to the 2019 Amazon fires was to offer funding to reforest these areas, rather than to address the core issues of enforcing laws, protecting lands of indigenous people, and providing incentives to landowners to maintain forest cover. The simplistic assumption that tree planting can immediately compensate for clearing intact forest is not uncommon. Nonetheless, a large body of literature shows that even the best-planned restoration projects rarely fully recover the biodiversity of intact forest, owing to a lack of sources of forest-dependent flora and fauna in deforested landscapes, as well as degraded abiotic conditions resulting from anthropogenic activities [Holl 2020: 581].