Four Principles of Forest Restoration
By: Thomas Crowther
Tags: Carbon Emissions, Biodiversity, Science, Conservation, Climate Change

As the world engages the Trillion Tree Campaign — a campaign originating with the United Nations Environment Programme and recently supported by the World Economic Forum to restore biodiversity and help fight climate change — it might seem like planting trees is an easy fix for our climate woes. Unfortunately, our ecological clock is ticking and, in my opinion, it will take an accelerated and multilateral approach to fight the effects of climate change. Planting trees alone is not enough to realise a positive impact for biodiversity, human well-being, and climate change. We need many solutions.

Wood wide web

In the Crowther Lab at ETH Zurich, we take a holistic approach to understanding ecological processes. Working with millions of direct observations, our team has mapped the complex web of fungi, bacteria, and root systems that connect trees — we call it the “wood wide web”. These maps help us to understand which types of ecosystems support certain types of trees and which species thrive in certain regions based on the type of fungi that exist.

“Our four principles of reforestation can help to ensure we are planting the right trees, in the right ecosystems and with local support to realise the greatest ecological benefit.” Tom Crowther

Our findings show that conservation and restoration of degraded ecosystems across the world -not currently in use by humans — have the potential to draw down vast amounts of carbon from the atmosphere without compromising urban or agricultural land.

The following four principles for reforestation can help to ensure we are planting the right trees, in the right ecosystems and with local support to realise the greatest ecological benefit.

Cut carbon emissions

First, participation in the Trillion Tree Campaign does not absolve us from the need to cut greenhouse gas emissions. Cutting emissions is the highest priority in the fight against climate change. We cannot offset all of our greenhouse gas emissions with trees alone. However, in combination with decarbonizing, the restoration of ecosystems can be valuable for drawing down some of the excess carbon from the atmosphere.

Plant trees in the right place

Second, we need to draw down carbon in an ecologically responsible way by planting native tree species in the places where they naturally exist. Planting trees in unsuitable ecosystems could result in unintended adverse consequences. Trees can warm the climate in many parts of the world, so a thorough, detailed, ecological understanding is critical for conservation and reforestation efforts to succeed. Preservation and restoration of natural forests, grasslands, shrub-lands and wetlands can serve as vital repositories of carbon and biodiversity. Monoculture plantations of exotic species will likely not yield the desired benefits.

Include local communities

Third, restoration implemented in a socially responsible and economically sustainable way is far more likely to succeed. Upholding the rights of indigenous people and local communities and building on fair and sustainable economic models is crucial. When local communities benefit from the services that those new ecosystems provide, restoration is sustainable.

Conserve old forests

Fourth, old forests are vital repositories of biodiversity and carbon. Yet, we are still losing them at an alarming rate. Conserving and sustainably managing existing forests is at the core of the global restoration movement. Restoring degraded regions can then help to tip the carbon balance in a favourable direction.

About the author

Tom Crowther

Professor Global Ecosystem Ecology at ETH Zurich and Scientific Advisor to the Trillion Tree Campaign.