Healthy forests and climate change

Most of my readers are well aware of my support for a national carbon fee and dividend climate policy. It is the single most effective climate policy available. A price on the carbon content of fossil fuels drives down carbon dioxide emissions from fossil fuels.

But there are other sources of carbon dioxide (like forest fires), other greenhouse gases (methane, nitrous oxide), and ways to remove carbon dioxide from the atmosphere (growing trees). So, there are other climate policies that complement carbon pricing.

In this column, I’m addressing how the way we treat forests can both decrease carbon dioxide emissions from forests and increase carbon removal by them.

As nations, corporations and even individuals look for ways to achieve ‘net-zero’ emissions of the greenhouse gases driving global warming, it is tempting to rely heavily on expanded natural carbon removal to offset emissions from fossil fuels (by far the largest source of emissions). Planting trees is one popular carbon offset. We all like trees, and growing trees remove carbon from the atmosphere via photosynthesis. What’s not to love?

Trees can be planted on land that has been degraded and abandoned or on land that is currently used for agriculture. Restoring degraded land to forest can, if done properly, offer ecological benefits in addition to the removal of carbon from the atmosphere.

But a recent estimate by the Land Gap Report1 found that only about half of the land required for the total of all offsets claimed by nations, corporations and individuals can be provided by restoration of degraded land. There simply is not enough degraded land with sufficient water available to meet all of the carbon offset pledges.

Trees can be planted in cities, which provides many benefits to residents and wildlife, but the area available is small, so the potential for global carbon removal is limited.

The rest would have to come from land already being used for agriculture. That would obviously restrict the supply of food, unless crops are planted between trees (agroforestry2), and meats in diets are replaced by plants, which require far less land.

The Land Gap report concludes that keeping existing forests healthy and intact is the most important contribution that land can make to both climate change and ecosystem health. Natural carbon removal from land already removes 24% of global carbon emissions3 from human activity, and the ocean removes another 17%. If deliberate burning of forests can be stopped and current natural removal can be sustained by preservation, then the carbon dioxide concentration in the atmosphere can be stabilized by reducing fossil fuel emissions to below the natural removal rate (i.e., 24% + 17% = 41% of current emissions). Restoration of degraded forests and further reductions in emissions from fossil fuels can then decrease the atmosphere carbon dioxide concentration to the level it was when our civilizations developed and flourished.

But how can deliberate burning of forests be stopped, healthy forests be preserved, and degraded forests be restored? The key is recognizing the service the forest is providing to humanity by sequestering carbon. The value of the service can be quantified using the social cost of carbon4 which estimates the amount of carbon they sequester each year. When an individual or corporation uses fossil fuel, they should pay forest owners (whether private, corporate, or national) for the service forests provide, according to the social cost of carbon and the carbon the fossil fuel user emits. This would make fossil fuel more expensive and healthy forests more valuable, driving down fossil fuel use and expanding natural removal of carbon. But the price of the carbon offsets5 must be based on sound estimates6 of the amount of carbon that forests sequester each year, so that forest owners don’t collect offsets for more carbon than they can actually sequester. A comprehensive system of tracking carbon offsets is required so that they are not double counted.

To summarize, preservation and restoration of forests can play important roles in stabilizing our climate, and forest owners should be compensated for the value their forests provide. But preservation will become more difficult as the climate warms, reducing mountain snowpack and increasing the likelihood of wildfires. We must stop deforestation and replace fossil fuel combustion as much — and as quickly — as possible (via carbon pricing), so that natural removal can continue to do its job in the natural carbon cycle.

Sources:

1. The Land Gap Report. landgap.org/wp-content/uploads/2022/11/Land-Gap-Report_FINAL.pdf
2. soilassociation.org/causes-campaigns/agroforestry/what-is-agroforestry
3. Drawdown Foundations. drawdown.org/drawdown-foundations
4. Social Cost of Carbon: What Is It, and Why Do We Need to Calculate It? news.climate.columbia.edu/2021/04/01/social-cost-of-carbon
5. Carbon Offsets. climate.mit.edu/explainers/carbon-offsets
6. The Carbon Sink Potential of Southern China After Two Decades of Afforestation. agupubs.onlinelibrary.wiley.com/doi/10.1029/2022EF002674

Climate scientist Steve Ghan leads the Tri-Cities Chapter of Citizens Climate Lobby.