Scientists around the world are working on new technologies to combat climate change, like carbon capture and solar radiation management, but could simply planting enough trees stave off some of the devastation?

We’re actually in the midst of an international effort to do just that, but researchers have found there are some flaws in our approach. In 2011, the United States, Brazil and many other countries around the world entered into a large-scale project to restore 150 million hectares of forest by the year 2020 and 350 million hectares by the year 2030 called the Bonn Challenge.

The project’s goal was to renew large swaths of “deforested and degraded” land, and a total of 56 countries have joined the cause since it was created. It was estimated that 350 million hectares of forest could soak up 1.7 gigatonnes of carbon dioxide every year.

We are on track to meet the goals set by the Bonn Challenge, but many climate experts have noted that much of the progress that’s been made won’t necessarily produce the intended climate benefits. A report from earlier this year that was published in the journal Nature found nearly half of the land that was pledged for forest area was “set to become plantations of commercial trees.” That means smaller, fast-growing trees that are grown to be harvested for paper, pulp and log make up much of what’s being counted as new forest area.

“If trees are harvested, it doesn’t take carbon out of the atmosphere for long before it’s put right back,” Richard Houghton, an expert in forest science at the Wood Hole Research Center, tells The Daily Beast.

David Milarch is a co-founder of the Archangel Ancient Tree Archive. This organization clones the largest and oldest trees from many different tree species around the world. They’ve cloned trees from over 130 different countries since the organization was founded 25 years ago, including the coast redwood, and they aim to “propagate the world’s most important old-growth trees before they are gone.”

Milarch tells The Daily Beast that if you want to get serious about tackling climate change, you need to be planting large trees that will be around for hundreds of years or more. He says planting smaller trees that will be harvested in the near future is “not doing anything for sequestering carbon.”

“You plant the right tree in the right place. You plant the strongest, hardiest natives state-by-state and region-by-region,” Milarch says. “You have to go about this very intelligently.”

Gordon Bonan, a senior scientist at the National Center for Atmospheric Research, tells The Daily Beast that reforestation and planting new trees are “essential components of climate change mitigation.” He says forests act as a “carbon sink to remove CO2 from the atmosphere.”

That said, some worry focusing too much on planting trees and restoring forests to fight climate change could be harmful. A study that was published in the journal Science in July claimed planting a trillion new trees would have a tremendous impact in the fight against climate change and could theoretically be accomplished. Many articles were written about what looked to be exciting news, but even the study’s lead author said this would not likely happen and shouldn’t be seen as a silver bullet in the fight against climate change.

“Reforestation is one possible way to address climate change, but the main thing we have to be doing is reducing greenhouse gases,” Karen Holl, a professor of environmental studies at the University of California, Santa Cruz, tells The Daily Beast. “It’s not a substitute.”

Holl says people shouldn’t get the idea that we can “plant our way out of climate change.” She says restoring forests and planting new trees are important parts of the equation, but reducing our greenhouse gas emissions is the top priority. Furthermore, she says we need to put a stop to the large amount of deforestation that’s taking place in the United States, Brazil and beyond.

“The most important thing is to be protecting existing forests, because they hold a huge amount of carbon both above ground and in the soil,” Holl says.

The planet lost over half a million square miles of forest between 1990 and 2016. President Trump issued an executive order at the beginning of this year that allows for more logging on public lands, and President Bolsanaro of Brazil has begun a logging campaign that will likely decimate the Amazon rainforest. New data shows the Amazon is losing roughly three football fields of forest per minute to deforestation.

Houghton says that reforestation and planting new trees are things that the U.S. should be doing much more actively, and he thinks we could stop subsidizing fossil fuels and use that money to pay for a large forest restoration project. It’s extremely unlikely this will happen during the Trump administration, but the experts we spoke with said it could be accomplished after 2020 if Democrats controlled the White House, both houses of Congress, and made it a priority.

“Getting off fossil fuels and getting into renewable energy will take some years, so in the interim, we could use some new forest,” Houghton said.