Yesterday, the Environmental Protection Agency announced that it would begin to count the burning of "forest biomass"—a.k.a. wood—as carbon neutral. The change will classify burning of wood pellets a renewable energy similar to solar or wind power.

In his statement, EPA administrator Scott Pruitt claims the change is a win for sustainable energy and the forestry industry. “Today’s announcement grants America’s foresters much-needed certainty and clarity with respect to the carbon neutrality of forest biomass,” he says. “Managed forests improve air and water quality, while creating valuable jobs and thousands of products that improve our daily lives.”

The problem is, as Chris Mooney and Dino Grandoni point out at The Washington Post, the carbon-neutral status of wood is fraught. While some researchers argue that using biomass as fuel passes the emissions test, others argue that it will only exacerbate climate change.

Here are five things to know about this controversial energy source:

Biomass is only sustainable on long time scales

The idea that forest biomass is carbon neutral is not wrong. Trees absorb carbon from the atmosphere as they grow. So if a tree is burned for fuel, the thinking goes, another can be planted to replace it. And then that replacement tree should eventually re-absorb the carbon.

But while burning wood immediately releases carbon, it takes decades or even a century for a replacement tree to absorb the same amount of carbon. In the meantime, all that atmospheric carbon will continue to drive climate change.

Forests need proper management to remain carbon neutral

Even if a tree is planted for every tree converted to fuel pellets, trees regrown on plantations don't store the same carbon as natural forests. One recent study suggests it would take 40 to 100 years for a managed forest to capture the same amount of carbon as a natural forest. And since most plantation forests are harvested at 20 year intervals, they will never make it to the carbon-neutral point.

There are also no guarantees, laws or regulations that require managed forests to grow to the carbon-neutral point, the Post points out. In fact, it’s even possible that cleared forest land could be converted to agricultural use, which would give biofuels a massive carbon footprint. Also not included in carbon calculations are all of the additional emissions released during logging and shipping the wood pellets across the globe.

“Unless forests are guaranteed to regrow to carbon parity, production of wood pellets for fuel is likely to result in more CO2 in the atmosphere and fewer species than there are today,” William Schlesinger, President Emeritus of the Cary Institute of Ecosystem Studies writes for Science.

Carbon emissions don't just come from burning

As Emma Grey Ellis at Wired reports, forest carbon is not just stored in their wood—a large amount is stored in the soil. And you can't take the branches without impacting the soil, Sami Yassa, senior scientist at the Natural Resources Defense Council, tells Ellis.

Soils can hold up to twice as much carbon as the trees above, depending on the type of forest and amount of leaf litter and debris on the forest floor. Exposing that material to more light and elevated temperatures spurs faster microbial breakdown of the soils and release of stored carbon. One 2017 study suggests forest soils are already giving off more carbon as the world warms.

“If a significant amount of that soil carbon is added to the atmosphere, due to microbial activity in warmer soils, that will accelerate the global warming process,” study author Jerry Melillo of the Marine Biological Laboratory says. “And once this self-reinforcing feedback begins, there is no easy way to turn it off. There is no switch to flip.”

The EPA has not yet completed its scientific analysis

As the Post reports, the announcement comes before the EPA’s Science Advisory Board has finished its deliberations. This is something that the EPA acknowledges in its press release, which states that the board’s process has not yet resulted in a “workable, applied approach.” But according to its policy statement on the matter, the EPA claims that the change will boost rural economies and the timber industry as well as reduce pests and wildfires.

As Miranda Green at The Hill reports, labeling biomass as "carbon neutral" has political element to it. Members of Congress have long pushed for this redefinition for economic reasons.

Reliance on wood could spark widespread clear cutting

The European Union is already relying on burning wood as a "carbon neutral" energy source to meet Paris Accord emission goals. And one of the big arguments used to support this switch to wood is that the industry would rely on the limbs, chips and sawdust produced by logging and milling that would already be incinerated. But in reality, that's not what's happening.

As Fred Pearce at Yale Environment 360 reports, the demand for wood pellets has sparked an increase in logging in the American south and across Europe. It's also fueled illegal old-growth logging in ecologically sensitive areas, including the Carpathian Mountains of Romania and national parks in Slovakia.

The demand for pellets is only increasing, Pearce reports, jumping 40 percent between 2012 and 2015 alone. As more climate-conscious countries, like Japan, South Korea and China begin to use this wood pellet “loophole,” logging will continue to expand, likely undermining the climate goals the regulations are intended to support.