Thread by @ForrestFleisch1

In the last week I've started to receive inquiries from people running tree planting programs wanting my help. I am suggesting that they shut down their programs. Here I will explain why:

Some context: A couple weeks ago a team I am a part of published a paper demonstrating the failure of long-term planting programs in India nature.com/articles/s4189… or ungated: conservancy.umn.edu/bitstream/hand…

This follows an earlier paper that discussed some of the common failings of tree planting programs more broadly: cedarhimalaya.org/images/Fleisch…

This work has received some attention in the press, and it seems like the folks who've been contacting me all read the same excellent story by @BenjiSJones vox.com/down-to-earth/…

The people who contacted me are in California and appear to be Silicon Valley businesspeople who are entranced with the idea of tree planting as a climate solution. I have no reason to doubt they are genuine & mean well.

Both have created web-based businesses where you can pay them to plant trees. The websites share a few characteristics. First, both clearly and directly reference the work of @CrowtherLab about a trillion trees as being their inspiration.

This is in spite of the serious doubts about the scientific validity of the trillion trees idea science.org/doi/10.1126/sc… and also goes against Bastin & Crowther's subsequent public statements.

But its actually quite consistent with their initial press interviews. Bastin, Crowther, and their coauthors still have alot of work to undo the repercussions of their exaggerated initial claims (which they have since disavowed, including in the Vox piece linked above)

Second, both websites make other dubious claims about tree planting. For example, one argues that planting more trees will increase the oxygen in the atmosphere.

This isn't really true - while oxygen cycles through trees on balance trees and forests are not really a net source of oxygen (because their decomposition uses up about the same amount of oxygen they create) and anyway, the planet is at no risk of running out of oxygen...

Third, both sites sell tree planting as a way to offset personal carbon emissions. There is alot of debate in my field about the validity of this kind of offsets, too much for twitter, but a few key problems are:

1. Land use change is already a major source of carbon emissions. The best way to think about forests absorbing new carbon is to think about this as offsetting carbon emissions lost from past forest destruction.

2. Relatedly, there isn't enough space on the planet for natural ecosystems to absorb more than a small share of fossil fuel emissions.

3. Trees planted today will absorb carbon in the future. Your emissions today start heating the planet today.

4. Tree planting projects often fail, so if you plant trees rather than reduce your emissions, you might actually be doing nothing.

A project whose goal is to plant a certain number of trees is particularly vulnerable to failure because its counting the wrong thing.

If the goal is to absorb emissions, we should count the carbon, not the trees. A few small large absorb more carbon than a bunch of little trees.

When we plant trees with carbon uptake or forest restoration as a goal, we don't try to maximize the number of trees. We try to maximize long-term carbon uptake, and this might actually mean planting fewer trees up front besjournals.onlinelibrary.wiley.com/doi/full/10.11…

In addition, if we focus on the number of trees, we lose sight of the relationships that support long-term forest sustainability. Do the people who live near the trees benefit from them? Do they get to make decisions about them? Will the site support trees in a warming climate?

If the company's goal is to plant a number of trees, they are less likely to pay attention to the broader context that supports long-term tree growth.

To me a focus on the number of trees, as opposed to, say, the well-being of the people growing the trees, the carbon stored in them, or the biodiversity they support, is a signal that the tree growing project is not well thought through. I can't support or advise such projects.

What to do instead? There are lots of organizations in the world working to improve land management in local contexts in ways that lead to win-win outcomes. More carbon, more biodiversity, and more human well-being. Oftentimes the key interventions aren't even biophysical

For example, sometimes better restoration outcomes might be the result of land reform, not distributing seedlings.

Maybe this doesn't lend itself to a nice marketing slogan, but I hope these efforts shift in this direction. What they are doing now appears to be at best a waste of time & money, and at worst a dangerous greenwash.

I'll just add that lots of these good programs DO plant trees. Planting trees is wonderful. The right tree in the right place brings many benefits. But the wrong tree in the wrong place is harmful. We should focus on our overall goals, not on the number of trees we plant.

And planting trees does not give you an indulgence to burn fossil fuels the rest of the day.

The guy who had this on his website is pointing out to me that oxygen concentrations used to be higher *but that was 200 million years ago* and the change wasn't the result of trees.