In a perspective published on 8 May in Science, Prof Karen Holl and Prof Pedro Brancalion argue that planting trees is not a simple solution to climate change and should certainly not be viewed as a solution by itself (1).
The authors write that alone planting trees won’t fix the underlying issues driving climate change. Moreover, tree planting initiatives can overshadows other actions that have greater potential for addressing the drivers of specific environmental problems, such as deforestation and greenhouse gas emissions.
“We can’t plant our way out of climate change”, said Professor Holl, a leading expert in forest restoration at UC Santa Cruz in the US. “It is only one piece of the puzzle.”
Trees and soil, of course, naturally take up and store heat-trapping CO2 gas from the atmosphere, which is why initiatives aimed at planting billions of trees are being promoted and carried out around the world as a nature-based solution to climate change.
“Trees are deeply entrenched in the human psyche”, Holl continued. “It’s very satisfying to go out and put a tree in the ground. It’s a concrete, tangible thing to do. But broad-scale tree planting initiatives must be undertaken carefully and with a commitment to long-term management if the benefits are to be fully realized”.
Far from a panacea
Tree planting can have both negative and positive ecological and social impacts depending on location and whether or not projects are comprehensively planned and evaluated.
“Planting trees is not a simple solution”, explained Holl. “It’s complicated, and we need to be realistic about what we can and cannot achieve. We need to be thoughtful and plan for the long term”.
While planting trees can improve biodiversity, water quality, and increase shade, the authors also warn that planting new trees in historic grasslands and savannas can disrupt native ecosystems and species, drain water resources, dispossess local landholders, and increase social inequity. Therefore, efforts should focus on protecting and maintaining intact forests instead of planting new ones.
Planting more trees is not the same as ‘increasing forest cover’
“The first thing we can do is keep existing forests standing, and the second is to allow trees to regenerate in areas that were formerly forests”, said Hall.
“Yes, in some highly degraded lands we will need to plant trees, but that should be the last option since it is the most expensive and often is not successful. I’ve spent my life on this. We need to be thoughtful about how we bring the forest back.”
Based on this, the authors outlined a set of principles to guide forest enhancement initiatives including reducing forest clearing and degradation, viewing tree planting as one part of multifaceted environmental solutions, balancing ecological and social goals, as well as effective planning, coordinating, and monitoring.
“Trees are a small piece of what needs to be a broader strategy”, added Holl. “We’re better off not releasing greenhouse gases to begin with”.
(1) Holl, K.D. and Brancalion, P.H.S. Tree planting is not a simple solution. Science (2020). DOI: 10.1126/science.aba8232