The Problem with Tree Planting Programs

Around the world, pledges to plant more trees in cities have taken off as a perceived "feel-good cure-all for global warming. In the U.S., conservative leaders like former President Donald Trump have touted tree-planting while working to eliminate emissions regulations." But the reality of planting trees is more complicated, write Feargus O'Sullivan and Linda Poon.

"Popular campaigns to plant 1 million trees are announced to much fanfare in cities from London to Los Angeles to Phoenix, Arizona, but often fall short of their goals. Many trees don’t survive, or thrive, or deliver their promised benefits." Although "[t]here is good reason for the enthusiasm around planting trees," including carbon storage and their ability to mitigate the effects of urban heat islands and pollution, "planting a massive number of trees is not necessarily a positive investment if not enough of them survive to become mature plants." Tree planting also comes with its own carbon cost, "meaning that trees have to survive years before they offset that cost. The largest environmental gain comes when trees mature, sometimes decades after they’re planted." 

The article details the lackluster performances of programs in Copenhagen and Los Angeles, where tree planting efforts ran up against a variety of unexpected challenges. According to U.S. Forest Service researcher Lara Roman,"[i]t’s not just about planting a million trees. It’s about planting and taking care of a million, and in the right places." For example, "non-native species can be the best choices in cities, where intense human activity has to an extent estranged climates from their broader surroundings."

"That’s why if cities really want to measure the success of their tree programs, they need to factor in the maturity and types of trees" by measuring tree canopy and planting diverse, resilient species.