Leaf 9: Is the Tree Bank Helping to Slow Climate Change?

A leaf from:

This Broken Land of Promise:

A Chronicle of Conservation in the Hispaniolan Border Country

I see this as an unavoidable question, given the nature of our work and the era in which we live.

My short answer is yes. We plant thousands of trees every year on lands that are mostly deforested, so we are increasing the amount of carbon stored in those lands. This happens because the trees absorb carbon dioxide from the atmosphere as they grow.

So far, so good. Next question: are tree-planting programs a remedy for climate change?

My short answer to this is no. Here are four reasons why not.

1. Forests have a limited appetite for carbon.

Young forests absorb carbon rapidly, but eventually the forest’s metabolism changes in several important ways: tree-growth slows; the amount of carbon deposited in the soil stabilizes; and the decay of dead wood and soil organic matter releases more and more carbon back into the atmosphere. At that point, the forest’s carbon budget begins to stabilize. The forest is still absorbing substantial amounts of carbon dioxide, but it’s also releasing substantial amounts. The results may vary from year to year, but a rough balance is likely to emerge, and that means no further net absorption until the process is reset by a major disturbance — a fire, or bout of logging, or a blow-down from a heavy storm.

Timber and wood-pulp plantations (which generally don’t merit the term “forests”) have a different kind of carbon budget, since they are usually logged and replanted on a schedule that is much more rapid than natural rhythms of forest loss and regeneration. So if you’re considering just the site itself, such a plantation may sequester more carbon than a forest, since the plantation’s net carbon absorption probably won’t level out before it’s cut and replanted. (But of course, a full accounting would have to track the wood that is harvested, and the fuel burned to manage the plantation and process the wood.)

2. Deforested landscapes often don’t want their forests back.

Formerly forested tracts of scrub or low-value pasture may look empty, but putting them back into forest can be very difficult, especially in the tropics. Owners don’t want to plant, or ownership is uncertain, or custody of the area is too weak to justify the effort. Ecological changes caused by deforestation — erosion, drying, changes in the soil flora and fauna, and so on — may make it difficult to reestablish trees. And there may not be adequate local sources of tree seed.

3. Plantations can be very thirsty.

Large-scale tree plantings are usually done, not to restore natural forest, but to develop plantations of one sort or another. Plantation development isn’t inherently a bad thing — we need rubber, palm oil, lumber, and paper. But large plantations often cause serious ecological damage, particularly in the tropics. One of the worst forms of damage involves changes in hydrology. Mass plantings of pines or eucalypts — the standard choices for softwood lumber and wood-pulp — can draw down water tables, thereby damaging neighboring forest and farmland, and the livelihoods of the people who depend on those lands.

4. The politics of this issue invites abuse.

Tree cover should not be used for political cover. Forecasting carbon draw-down from plantation development is no substitute for failing to protect natural forest, failing to account for the damage that fossil fuels are doing, or failing to promote renewable energy.

I love trees, and I love growing them and planting them. But I recognize that tree-planting is not inherently benign. Is a particular project environmentally beneficial or not? That depends on where the planting is, what was growing there before the planting went in, what kinds of trees were planted, and how the area is being managed afterwards.

Planting huge numbers of trees is not necessarily a good thing. Enormous monocultures of alien tree species usually do great ecological damage, and may foreclose opportunities for restoring native forest. Direct displacement is even worse: plantation development has destroyed millions of acres of forest — a type of deforestation by tree-planting that continues today.

What about the Tree Bank itself? How much carbon is our project putting away? I tried to figure this out a couple of years ago, but I could not find estimates that were both solid and relevant. Carbon sequestration varies considerably from one forest to another, and as far as I could discover, carbon stocks have not been assessed in the Tree Bank’s program region. The closest assessments that I could find were for forests in Puerto Rico and various locations in Central America. I’m sure that we’re doing some good on this front, but our soils are thin and our forest canopies are relatively low, so maybe not a lot. But every ton of sequestered carbon counts.

So, yes, the Tree Bank is helping to slow climate change through tree-planting. That’s important, and we should do more of it — in a green way, of course! But the remedy for climate change is renewable energy.

“This Broken Land of Promise” is my attempt to describe and interpret our Tree Bank Hispaniola program. I welcome your comments and questions. Please write me in the comment box below or email me at cbright@earthsangha.org.

About quotations: I try to quote people as accurately as I can, but conversations sometimes occur in distracting circumstances, and my memory is far from perfect. An additional complication when quoting our Dominican colleagues and friends: these people speak only Spanish, so our conversations with them are always in that language. For the most part, translating these exchanges is not difficult, but sometimes a literal rendering would make for poor English; in such cases, my aim is to capture the speaker’s tone and meaning, rather than his exact wording.

— Chris Bright