And the exact amount of carbon they remove can vary quite a bit depending on variables like vegetation health. “One of the main risks of some of these biology-based proposals is that it is assumed that X number of trees can be easily equated to X million tons of carbon without really looking at what types of trees they are and where they are. “. it’s being planted, ”says Cox. The amount of carbon captured could end up being negligible.“ You have a lot of trees, which is great. You don’t necessarily get the benefits of climate change. “
Another technique known as carbon capture and storage bioenergy, or BECCS, is also based on monoculture, usually fast-growing herbs. In this case, the vegetation is burned to produce energy, and the resulting emissions are sequestered underground. But it also comes with its own set of dubious side effects: it would require large tracts of crops and large amounts of water to affect atmospheric carbon concentrations: an article published last month found that only in the US, the climbing. up BECCS would expose 130 million Americans to water stress by 2100.
But in a global climate that is going crazy, there are even risks to restoring forests to their former glory, because that glory is increasingly dangerous. Overfed forest fires are now destroying forests, rather than gently restoring ecosystems to give way to new growth. If you spend a lot of time and money restoring one of these forests to sequester carbon, and then burn it, all that carbon goes back into the atmosphere. Or if the political regime of a given country changes, and goes from supporting reafforestation a ofafforestation, you would have the same problem. Just look at what’s happening on Amazon.
“I would say a lot of land removal proposals could be risky,” Cox says. “Because you have a very, very high risk that carbon sequestration won’t happen in the first place, or that it will happen, but after 10 years it’s reversed.”
The dreaded “moral hazard”
Researchers have developed a way to mimic natural carbon sequestration with a technique called direct air capture or DAC. These machines suck in air, pass it over the membranes to remove carbon dioxide, and pump it underground, shutting it down forever. The tide may be shifting towards the DAC in the US. Last month, the Biden administration invested $ 3.5 billion to support direct air capture. (This comes five years after a California congressman introduced a bill that would fund geoengineering research, but it never got anywhere.)
But this also faces two major problems. The first is that DAC does not exist anywhere on the scale needed to make a dent in excess atmospheric carbon. A plant that went into operation in Iceland last year is only capturing the equivalent emissions of 870 cars. A 2021 study estimated that it would take an investment of 1 to 2% of the world’s gross domestic product to capture 2.3 gigatonnes of CO2 a year to 2050, and that’s only a fraction of the current annual emissions, which are around 40 gigatons. “There is a risk that we may not be able to scale and deploy fast enough,” says Benjamin Sovacool, who studies the risks of geoengineering at Aarhus University in Denmark. “It seems like the pace at which we should deploy them is different from any previous energy transition we’ve had, because the scale is so immense.”
The second problem is the “moral hazard”, or the temptation to rely on the DAC as a crutch, instead of doing what needs to be done: drastically reduce greenhouse gas emissions. If a nation’s leaders anticipate being able to eliminate emissions through the DAC, they don’t have to worry about reducing those emissions in the first place. It is like waiting for a miracle antiviral, unless the required dose does not yet exist.
There is a possibility that the extreme and desperate nature of geoengineering will do the opposite: instead of encouraging complacency or confidence in state-of-the-art technology solutions, it may alarm the public enough to start treating climate change as an emergency. . But, says Sovacool, “politicians could be even more susceptible to moral hazard, because they only think in current terms. They will be happy to push as much as they can for future generations.”