Grand global commitments to plant trees to fight climate change are welcome. Healthy landscapes that suck planet-heating carbon out of the atmosphere – locking it into forests and soils – are among the best technologies there are yet to bend the Keeling Curve in a new direction. Tree planting is no alternative to ending the burning of fossil fuels, but along with zero deforestation, restoration can draw carbon out of the atmosphere while simultaneously benefiting biodiversity, food security and livelihoods.
But where to begin? Many landscape restoration projects do not get off to a good start, jeopardizing their chances to make a long-term positive impact. It’s not just a simple as planting saplings and letting nature take over. Is the soil badly compacted from decades of cattle grazing? How eroded or nutrient-deficient is the ground? What, exactly, are your aims for a particular restoration project? And, especially in the hyper-diverse tropics, are you selecting the correct tree species?
Answering these often-overlooked questions can be the difference between a successful restoration project and a failed one. A new tool developed by scientists at the Alliance of Bioversity International and CIAT (and colleagues around the globe) can help. The Diversity for Restoration (D4R) tool is a straightforward, five-parameter survey that tailors the choice of tree species and seed sources to location, objectives and local environmental conditions in tropical forests. Originally designed for the dry forests of Colombia, the tool now works for Peru, Ecuador, Burkina Faso and Cameroon. More countries will be online soon.
The tool’s description was published in the Journal of Applied Ecology.
“Governments in many countries are all announcing big plans about tree planting but they cannot always execute these plans effectively,” said Chris Kettle, an Alliance scientist and co-author. “The D4R tool facilitates on-the-ground decision-making that cannot be provided by satellite-based tools that, while very useful to land management and forest monitoring, do not provide the information that is needed to make sure that the selected tree species match the local site conditions and restoration objectives put forward by the restoration initiative, taking into account local cultural, political and environmental considerations.
The right questions
D4R is not just a guide to the technical aspects of restoration. Crucially, it makes prospective landscape restorers think about more than just the biophysical aspects of restoration. One reason restoration projects are not always effective is because they do not always consider landowners, local customs and the specific objectives of restoration.
Unless the objective is “natural” ecosystem restoration via the propagation of native tree species on land free of people and livestock – ideally from seeds brought in by bats, birds and small mammals from a large, adjacent protected reserve – a restoration project needs careful planning, execution and monitoring.
“With an unprecedented amount of new restoration commitments and investments coming online, there will be many new players getting into this without much knowledge or prior experience,” said Evert Thomas, a co-author from the Alliance. “And climate change also makes restoration more of a challenge. It’s more important than ever to select the species that are most likely to survive the critical, early phase of restoration for any project to be a long-term success.”
Objectives can run the gamut from the “simple” expansion of protected forest reserves to intensification of silvopastoral farming systems that integrate trees for fruit and timber, livestock, soil-improving shrubs and grasses and produce.
“If outside donors come in with plans to plant trees, and tree species choices don’t match with what people really are interested in, then there’s a high risk that the project will be abandoned and become a failure,” Evert said. “The tool not only takes into consideration selecting the right species based on what’s possible in a place, taking into account climate change, functional traits, genetics and what have you. But it does this in a way where local stakeholders can focus on their objectives. Do I want to store carbon and promote wildlife? Do I want to harvest firewood and protect my watershed? What risks factors does my location have? Is there soil erosion or cattle that will eat my seedlings?”
Seeing the data for the forest
Even before the start of the UN Decade of Ecosystem Restoration, which runs through 2030, major commitments to restoration were made under the Bonn Challenge, a 2011 initiative of the German government and the International Union for Conservation of Nature. More than 200 million hectares have been pledged, which has created ample material to study how well restoration projects are going. The data can inform new commitments, and D4R helps organize this knowledge.
“Compiling and combining all this knowledge for decision-makers is really a lot of work,” said Tobias Fremout, the study’s lead author and scientist at KU Leuven. “D4R is doing a bit of that work for them by integrating all types of data into a format that’s really easy to use.”
The tool also helps restoration planners to tap into local biodiversity, instead of solely relying on the typical go-to species of tropical forest restoration such as teak, eucalyptus and pine. While nonnative species often play a critical role in producing valuable timber forests, many of the tens of thousands of tropical tree species that can contribute to better restoration are increasingly better understood.
“With this tool, we’re trying to make sure that lack of knowledge on lesser-known species is not an excuse to have less diversity in restoration projects,” Fremout said.