Spatially explicit econometric studies… say that five times fast.

My guests on this week’s Wonkcast are CGD’s Jonah Busch and Kalifi Ferretti-Gallon, who have conducted a meta-analysis of 117 such studies to discover what drives deforestation—and what actions slow or prevent it.

Their ambitious study, the first to use this approach on such a large scale, covers two-thirds of the world’s tropical forests. For those who want to cut to the chase, this CGD brief offers a succinct summary of the findings.

In the Wonkcast we discuss why a development-oriented think tank like CGD is tackling deforestation: because intact forests provide many benefits to poor people, and because deforestation is an important driver of climate change, which in turn undermines development efforts. We then unpack the study’s main findings.

Kalifi, who did most of the number crunching, explains the criteria for selecting the 117 studies included in the meta analysis, and how she and Jonah then distilled the many factors that may drive or slow deforestation into 40 variables.

The big take-aways:

“Keeping roads out of an area, making sure that road networks are planned in a way that connects people, gets them to market but doesn't open up new frontier areas of remote forests” helps to protect the forest,” Jonah tells me.

Similarly, designating protected areas has frequently been effective. While many of these are in remote or especially scenic areas, Jonah says the meta-analysis showing that they have been effective suggests that designating more protected areas in places that are subject to deforestation pressures holds promise.

Among the surprises: strengthening land tenure and community forest management projects—two popular approaches to slow deforestation—were not proven on balance to be effective.

“I was expecting to see that community forest management lined up with less deforestation,” Jonah says. “If this were the case it would be a nice win-win for local economic development and forest protection…But while there were slightly more cases where community forest management was associated with less deforestation rather than more deforestation, it wasn't a statistically significant difference.”

In contrast, he says, payment for ecological services, for example, by paying a community to protect a forest watershed, tended to work, although the approach is comparatively recent so there are relatively few studies of such efforts.

We end the Wonkcast with a discussion of the links between the findings of the new meta-analysis and REDD+, the global effort to reduce emissions from deforestation and forest degradation.

For more on REDD+, see the CGD initiative Tropical Forests for Climate and Development, of which Kalifi and Jonah’s new meta-analysis is an important contribution.