by Robin Chazdon, Bruno Calixto, Mariana Oliveira, Jared Messinger, Julio Alves, Miguel Calmon and Will Anderson
When you think about restoring a deforested patch of land, you likely picture someone digging holes in the ground and planting seeds or saplings. Planting trees is important (if it’s done the right way), but in many cases, it’s better and cheaper to let trees grow on their own and forests restore themselves with little human assistance.

In fact, there is a wide spectrum of approaches to restoring forest landscapes. At the passive end, there is spontaneous regeneration, where trees and other native vegetation regrow naturally on the land. Think about what happens after a normal forest fire: after some time, little shoots pop up from the ash and grow into big, strong trees without any help from people.

On the other end of the spectrum is the most commonly known approach, where people collect seeds from the forest, produce saplings in nurseries, and plant and maintain trees in degraded forests and lands.

Between those two extremes lies a particularly promising and viable approach: assisted natural regeneration, or ANR. What is Assisted Natural Regeneration?

Assisted natural regeneration is a blend of active planting and passive restoration, where local people intervene to help trees and native vegetation naturally recover by eliminating barriers and threats to their growth, leaning on their knowledge of the land and on ancestral traditions.

But what exactly can people do to help the land and limit the frequency and severity of disturbances that can harm young trees and prevent them from growing?

To prevent the spread of wildfires, people can build firebreaks and clear the forest floor of dry debris. To stop cattle from munching on saplings, they can build fences to keep them out. To give native trees enough room to grow, they can remove invasive grasses and shrubs. And, if natural regeneration on its own does not increase tree cover quickly enough or the targeted species fail to pop up on their own, people can selectively plant trees to fill the gaps.

So why is ANR an important technique in the ecosystem restoration toolkit? And what are its specific advantages? Research shows that ANR is a cost-effective, nature-based solution for restoring millions of hectares of land, while providing the ecosystem services — like clean water and healthy soil — that people need to thrive.
What Are the Advantages of Natural Forest Regrowth?

Assisted natural regeneration can play a critical role in achieving global targets on climate and biodiversity, including the Paris Climate Agreement, the Trillion Trees initiative, and ambitious targets set by the Bonn Challenge — which aims to restore 350 million hectares of degraded and deforested lands by 2030.

More than 60 countries have already committed to revitalize 210 million hectares (or 519 million acres, more land than all Saudi Arabia) through the latter. That may sound like an astronomically large area, but it’s still only a small portion of the more than 860 million hectares (2.1 billion acres) across the tropics — an area the size of Brazil — that could benefit from restoration.

Achieving those massive goals is simply impossible without embracing the power of regrowth. Why?

First, trees and forests can be restored using ANR at less than a third of the cost of tree planting, based on WRI estimates.

Second, ANR can restore much more land, much more quickly than active planting, as it requires very little human intervention. In Niger in Africa’s dry Sahel region, farmers have used ANR to regenerate more than 200 million trees since the 1980s. Read further from the source above