Planting Trees - Shutterstock

This article was originally published on July 10, 2019.

Last week, a new study in the journal Science highlighted the role that forests can play in tackling climate change. Researchers have estimated that by restoring forests to their maximum potential, we could reduce atmospheric carbon dioxide (CO2) by 25 percent, a step that would take us back to levels not seen in more than a century. While the study offers hope in the fight against climate change, other experts warn that the solution is not so simple.

The study, led by scientists at ETH-Zürich, Switzerland, found that there are 0.9 billion hectares of land on the planet available for more trees – an area the size of the continental United States. Converting these areas to forests would be a game-changer for climate change, the authors suggested.

Read more: We have lost 35 percent of our forests in the last 300 years

“[The study] is probably the best estimate we have so far of how much land can support tree cover on our planet,” says Robin Chazden, a forest ecologist and professor emeritus at the University of Connecticut, who was not involved in the study, but she is quick to note that reforestation is not as simple as it sounds.

“Not all areas that can be forested necessarily need to be forested,” says Chazdon. Taking local ecosystems into account, as well as the impact of trees on nearby communities, is essential to making global tree restoration viable. In other words, fighting climate change with carbon-sucking trees requires more planning and strategy than simply planting trees wherever we can.

Does planting trees help stop climate change?

According to Science authors of the paper, only six countries – Russia, the United States, Canada, Australia, Brazil and China – hold more than 50 percent of the global tree restoration potential. If all the areas they identified were restored, they estimate that an additional 200 gigatons of carbon could be sucked out of the air and locked in the tree. That number, the authors say, represents two-thirds of historical human-made carbon emissions.

Regions identified by Bastin and colleagues where trees could be planted, after excluding desert, agricultural and urban areas. Blue denotes areas of highest potential. (Credit: Bastin et al. 2019 Science)

But Zeke Hausfather, an analyst for the climate news website Carbon Brief, disputed those conclusions on Twitter shortly after the study was published. Referring to the latest report of Global Carbon Project — which estimates cumulative carbon emissions from human activities at roughly 620 gigatons — Hausfather pointed out that Bastin’s forecast may actually represent only a third of historical emissions. It’s a reminder that the problem may require more than just planting trees, he says.

“This is not to say that reforestation is not an important mitigation strategy, just to caution that like any other climate solution, it is part of a larger portfolio of strategies and not a silver bullet,” Hausfater concluded.

Environmental considerations: Planting trees to mitigate climate change

In 2011, Germany launched Bonn Challengea global initiative aimed at restoring 350 million hectares of trees by 2030. So far, nearly 50 countries have signed to the commitment. But approximately 10 percent of them do not have enough available space to restore the planned amount of trees. Unless, you know, they’re planting in places that aren’t meant to be forests.

(Credit: Tamara Kulikova/Shutterstock)

The consequences of putting trees where they don’t belong can be serious. Inappropriate flora can kill native ecosystems, weaken biodiversity, dry up water supplies and make areas more prone to fire. Countries like Japan and Ireland are already experiencing the consequences of poorly planned tree planting initiatives. The use of only one or two tree species for replanting in these countries has led to ecological disruption.

Jean-Francois Bastin, lead author of Science study, agrees with the importance of respecting native species when restoring ecosystems. “We are not talking about reforestation, planting or reforestation. We are only talking about restoring natural ecosystems,” he emphasizes. His study does not provide information on what trees to plant, but he says they are working on developing a list of recommendations for different areas.

Is it still possible to plant trees?

Achieving the huge carbon reduction claimed by Bastin and his colleagues with trees alone is a technical challenge. Every possible identified parcel of land must be completely covered with trees. This is unlikely, given that the countries will lose their economic potential as the land is covered – something politicians may not want to do. In addition, areas along international borders can present logistical challenges. Not to mention the costs of large-scale reforestation projects, a limitation not considered in the study.

In addition, it will take many decades before the new forests become mature enough to store large amounts of carbon. But as Bastin’s own research suggests, time is of the essence, as climate change will progressively reduce the areas available for trees to regenerate. Based on their model, more than 220 million hectares of potential forest could be lost by 2050 if climate change continues at its current rate.

While nations around the world discuss planting trees to alleviate climate change, deforestation in tropical forests continues to grow. (Credit: Richard Whitcombe/Shutterstock)

Another issue is the type of wood used. An earlier study published in Nature found nearly half of all recovery commitments from the Bonn Challenge are in the form of plantations, which are not the best for carbon storage. Simon Lewis, a forest ecologist who authored the analysis with colleagues from University College London and the University of Edinburgh in the UK, fears that plantations will have little impact on climate change.

“Forests should be natural forests that will remain long-term, not plantations that are harvested every decade,” Lewis says. “Because, yes, plantations have rapid carbon uptake as the trees grow. But as soon as those trees are used, much of that carbon is released back into the atmosphere.

Louis too rejects Bastin’s co-author Thomas Crowther’s claim that “reforestation is the best solution to climate change available today.”

“This is absolutely not right. The best solution to climate change is to keep fossil carbon in the ground,” says Lewis. Other experts have also expressed concern that Bastin’s research is being hyped misconceptions about the problem and the underlying solution, which can be problematic in the long run. They fear that the emphasis on planting trees could distract policymakers from other efforts to reduce carbon emissions and stop climate change.

The Rainforest Solution

In another study published last week in the journal Scientific progress, Chazdon and colleagues argue for a more focused approach than simply planting trees to stop climate change. They say focusing on tropical rainforests is a more effective means of stopping climate change using trees. They considered both available space and cost-opportunity factors that would make recovery most feasible in what they called “recovery hot spots.”

“Those are kind of the low-hanging fruit, the most obvious places to start,” says Chazden. Brazil, Indonesia, India, Madagascar and Colombia top the list of countries with the most recovery hotspots.

The study adds to the body of literature calling for action to protect and restore natural forests, particularly in the tropics. But despite global efforts to reduce deforestation, logging and clear-cutting are increasing in the Amazon, the world’s largest rainforest. New satellite images show areas bigger than a football field are cleared every minute.

“We’re kind of working against the clock here. But at the same time, I think we should not only think about quick fixes, but simply about mass tree planting programs,” says Chazden. “We really can’t afford to fail.”

Source link

Leave a Reply

Your email address will not be published. Required fields are marked *