A couple months ago I was on a hike in the White Mountains with my family. My mom handed me a small acorn she had found on the on the forest floor. I looked up and saw a Hemlock tree from where it had fallen, towering 100 feet tall. While most people learn about photosynthesis as a child, it’s still remarkable that something less than half an inch can grow so large with three basic elements: sunlight, carbon dioxide (CO2) and water. For millennia, trees have spread around the globe and played a critical role of providing oxygen and valuable ecosystem services ranging from a home for animals, holding back deserts, retaining water, providing shade, and acting as a natural filtration for pollutants. It is no wonder that oftentimes people follow the simple logic of tree planting as the most obvious climate fix. Plant a tree. Take back carbon from the atmosphere. Count it as a ton of carbon sequestered. While indeed this can be true, it is not always that simple. There are a number of issues to consider when we use trees as the dominant way to manage carbon we are responsible for emitting.
The way in which different carbon pools change over time matters
The answer to this question is the holy grail of managing the stock of carbon with natural processes. Trees hold the most amount of carbon on land – almost at least 40% of carbon in the biosphere. The Orbiting Carbon Observatory (OCO), a NASA project which uses a satellite to detect global CO2 levels with through light sensing tools, recently reported some troubling news from OCO2 through a technical publication in Nature. During the El Nino event of 2015/16 a massive amount of carbon was released from the topics that was not recovered. They were able to detect an abnormal rise of 3 parts per million rather than the typical 2. The troublesome news shows that even though anthropogenic emissions were flat at 2 ppm, the data show a 50% increase in atmospheric carbon. What this means is that the degree to which we can rely on biological processes to sequester carbon is in serious question. This concern is exacerbated by an often forgotten fact:
Only about half of the greenhouse gases that we emit end up in the atmosphere.
Only 25% of this half, or between 4-5 parts per million are absorbed by the biomass – the rest is absorbed by the oceans (another post on that coming soon).
The type of biomass matters
When counting carbon, different methodologies are able to stratify – or separate certain kinds of biomass as a carbon stock. However there are a number of issues to take into consideration:
- Will invasive species change the carbon balance?
- Will the biomass die because of drought?
- How susceptible is the land to forest fire? insects?
- Will the addition of trees cause more benefit or harm to the specific location?
- Could this work with agroforestry?
Where to stop deforesting vs. reforesting matters
There is a much greater value to not cutting down trees – particularly old growth forests than to planting new ones. The incredible productivity of the rainforests will not come back for decades, if ever. The slash and burn of ranchers has devastated the land and depleted the soils of much of the organic matter. The REDD+ program has a good model to pay people to not cut down trees, but needs strengthening such that it is possible to ensure that it happens for an indefinite period of time. This creates a really high enforcement cost.
For people to get paid to remove carbon, they have to prove that they wouldn’t have otherwise done it. For some forests, this isn’t a problem because the trees would have grown naturally. The U.S. Forest Service has made a useful forest generation visualizer that can set a baseline of total forest stock. If it is a new practice that is not currently being done, it can be counted for as additional. It could also be considered additional if someone was already doing it – i.e. soil carbon sequestration, but now they realize they can get paid for it, they are incentivized to do more of it.
The regenerative movement is a great opportunity to activate land based approaches that can be used by farmers and other stewards of a land to more efficiently manage it as not only a carbon sink, but also a more productive way of interacting with the land. This can include:
- Farming practices that require no fertilizer, store more water, and don’t require tilling in addition to removing massive amounts of carbon
- Rotational grazing with cattle to eat grass at the apex – storing more water and improving carbon content
On a different part of the trail in the White Mountains, I looked out and noticed that almost all the ash trees were dead, or dying. In 2002, the Emerald Ash Borer first appeared in the United States. Since then over 24 states have been affected with the insect which when it hits an area causes 50% of the species to die off at once. The California pine beetle has created a similar problem in the western United States and also creates the conditions for forest fires. The explosive fires in California should be a reminder: wood can burn.
There is a double edged sword to relying on biomass alone as the solution to reversing climate change.
Deforesting is a problem. The carbon that is released from this action should be counted as an externality by those who do it. Ranchers who slash and burn should be responsible for replacing the emissions. They should be held accountable, and pay for cutting down trees when the carbon is released.
If the recent data from the NASA study should tell us anything, it is that we can’t count on the natural carbon cycle to clean up after ourselves. Furthermore, we already know that massive amounts of methane are being released from permafrost. Who is going to take responsibility for pulling that back?
Yet the truth is that even if no one wants to take responsibility for excess carbon dioxide in the atmosphere, we are all collectively stuck with the bill. If we want to live in a world that has avoided the most devastating effects of climate change we have to pay it. It will require all options that can remove and permanently store carbon. The good news is that it is possible, sometimes economical, and we can do it by managing and increasing the total stock of bio-sequestration, industrial sequestration and ocean sequestration.
Also published on Medium.