As global population swells and the push to grow more food increases, forests often find themselves on the losing side of the equation.
The leading cause of deforestation across the globe is conversion to cropland or pasture. In the Amazon basin alone, conversion from tropical forest to cropland for soy production resulted in the loss of 80 million hectares of forest as of 2012.
And yet, the pace of agricultural expansion shows no sign of relenting. Instead, some studies estimate that in order to keep pace with population growth, land used for agriculture will need to expand by more than 740 million acres — an area larger than India.
Those numbers left researchers at Stanford University’s Woods Institute for the Environment with a question: If agricultural expansion — and deforestation — have to take place, does it matter how it’s done?
A new study says yes. Published earlier this month in the journal PNAS, it found that the way that deforestation occurs can have a huge impact on environmental losses, especially with regard to carbon storage and biodiversity.
“The goal should surely be to deforest less,” Rebecca Chaplin-Kramer, a research associate at the Stanford Woods Institute for the Environment and co-author of the study, told ThinkProgress. But when deforestation must occur, she wondered, “Is there a way to avoid extreme impact?”
To get their results, Chaplin-Kramer and her colleagues looked at various deforestation scenarios in the Matto Grosso region of Brazil, one of the country’s largest soy producing regions. Using landscapes both real and theoretical, the researchers imagined what would happen if agricultural expansion happened along the edge of a forest, in the center of a forest, or in segments that fragment the forest into smaller pieces.
What Chaplin-Kramer and her colleagues found was that some deforestation methods are worse than others. For example, deforestation that occurs in a fragmentary pattern — like when a road is plowed through a forest and cropland is created off of that road — causes very steep losses in carbon storage and biodiversity, especially in the early stages of deforestation. When deforestation occurs in a fragmentary way, crucial corridors used by wildlife can be blocked, hindering wildlife’s ability to seek food, shelter, and mates.
On the other hand, deforestation that occurs at the edges of a forest and in consolidated patches reduces biodiversity losses by more than three times and preserves carbon storage by an order of magnitude, the study found. That’s because forest edges tend to store less carbon than trees deeper into a forest, because forest edges generally suffer higher mortality rates due to threats like wind damage, pests, or fire.
“There have been, especially in the Amazon, a few field studies that shows less carbon is stored in source edges because of wind edges, and in general, it’s thinner at the edges,” Chaplin-Kramer said. But the researchers were surprised to see just how much of an impact forest edges make on preserving carbon storage and biodiversity in deforestation scenarios.
“It’s so much deeper than what we’ve measured in the field, and it’s so pervasive,” Chaplin-Kramer said.
Chaplin-Kramer and her colleagues were so surprised by their findings that they expanded the study to look at deforestation patterns all across the tropics. That research, which Chaplin-Kramer says will be submitted soon to the journal Nature, found that the trends seen in Matto Grosso hold true for tropical forests around the world.
“It is very consistent across the tropics. It varies a lot depending on climate and human influences, and how deep the edge effects penetrate, but we do see these edge effects consistently throughout the tropics,” she said. “This isn’t just about Matto Grosso. We need to think about it much more broadly when we think about tropical deforestation.”
Chaplin-Kramer hopes that the findings encourage food corporations to think about how their sourcing impacts deforestation. In recent months, companies like Archer Daniels Midland, one of the world’s largest traders of agricultural commodities, and McDonald’s, the world’s largest fast food company, have made sweeping pledges to end deforestation in their supply chains.
But even if companies can’t end deforestation completely, Chaplin-Kramer notes that it’s still important to look at how agricultural expansion takes place in their supply chains.
“What we’ve learned from this is that it matters, so it’s worth paying attention. It’s worth looking at past trends and asking where the agricultural expansion has happened,” she said. “While [food companies] don’t get to say necessarily, ‘Don’t fragment your forest,’ they could certainly provide incentives.”
A previous version of this post stated that Stanford researchers estimated that agricultural land use would expand by 740 million acres. In fact, those numbers come from a different study. ThinkProgress regrets the error.