Nothing Is Simple In Reforestation, As Opposed To Simplistic "Plant Trees!" Dressed Up As Policy

[hatrack]

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Conservationists are understandably eager to harness this enthusiasm to combat climate change. “We’re tapping into the zeitgeist,” says Justin Adams, executive director of the Tropical Forest Alliance at the World Economic Forum, an international nongovernmental organization based in Geneva. In January 2020, the World Economic Forum launched the One Trillion Trees Initiative, a global movement to grow, restore and conserve trees around the planet. One trillion is also the target for other organizations that coordinate global forestation projects, such as Plant-for-the-Planet’s Trillion Tree Campaign and Trillion Trees, a partnership of the World Wildlife Fund, the Wildlife Conservation Society and other conservation groups.

Yet, as global eagerness for adding more trees grows, some scientists are urging caution. Before moving forward, they say, such massive tree projects must address a range of scientific, political, social and economic concerns. Poorly designed projects that don’t address these issues could do more harm than good, the researchers say, wasting money as well as political and public goodwill. The concerns are myriad: There’s too much focus on numbers of seedlings planted, and too little time spent on how to keep the trees alive in the long term, or in working with local communities. And there’s not enough emphasis on how different types of forests sequester very different amounts of carbon. There’s too much talk about trees, and not enough about other carbon-storing ecosystems.

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Just how many more trees might be mustered for the fight is unclear, however. In 2019, Thomas Crowther, an ecologist at ETH Zurich, and his team estimated in Science that around the globe, there are 900 million hectares of land — an area about the size of the United States — available for planting new forests and reviving old ones (SN: 8/17/19, p. 5). That land could hold over a trillion more trees, the team claimed, which could trap about 206 billion tons of carbon over a century. That study, led by Jean-Francois Bastin, then a postdoc in Crowther’s lab, was sweeping, ambitious and hopeful. Its findings spread like wildfire through media, conservationist and political circles. “We were in New York during Climate Week [2019], and everybody’s talking about this paper,” Adams recalls. “It had just popped into people’s consciousness, this unbelievable technology solution called the tree.”

To channel that enthusiasm, the One Trillion Trees Initiative incorporated the study’s findings into its mission statement, and countless other tree-planting efforts have cited the report. But critics say the study is deeply flawed, and that its accounting — of potential trees, of potential carbon uptake — is not only sloppy, but dangerous. In 2019, Science published five separate responses outlining numerous concerns. For example, the study’s criteria for “available” land for tree planting were too broad, and the carbon accounting was inaccurate because it assumes that new tree canopy cover equals new carbon storage. Savannas and natural grasslands may have relatively few trees, critics noted, but these regions already hold plenty of carbon in their soils. When that carbon is accounted for, the carbon uptake benefit from planting trees drops to perhaps a fifth of the original estimate.

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https://www.sciencenews.org/article/planting-trees-climate-change-carbon-capture-deforestation

[Pobeka]

1. If you want more wood volume, plant more trees per acre, up to a point.

There is a phenomena in plants, where they will actually grow faster if they are nearer each other.

It is well researched and documented -- happens over many species.

But eventually they will hit a resource wall -- light, nutrition or moisture will be limiting after 10 or 15 years (with trees), and there will be individual trees starting to die.

The other thing that makes it complex is you'll need to think about different species than were natively found in an area. For example in the pacific northwest of the USA douglas-fir and other conifers may not be heat and drought tolerant enough to survive the new conditions they face in an altered climate.

--- just a couple of thoughts...

[NickB79]

2. Too many tree planting schemes are just super-sized cornfields

Monocrops of one non-native species in rows. Typically pine trees that are conveniently also good for lumber. Not that anyone would DREAM of harvesting these trees in the future......