Trees? Made of carbon. Good soil holds a lot of carbon. Plants draw carbon dioxide out of the atmosphere.
It's well-known that the trick to reducing net carbon emissions relies on not emitting so much of the stuff and finding a way to get it back where it belongs.
That's where the land comes in. Thirty percent of greenhouse gases come from "the land-use sector." The land holds thrice the amount of carbon polluting the atmosphere. So let's talk farming. Let's talk trees. And let's talk land degradation.
That's the argumentative thread running through the Worldwatch Institute's newest report, Mitigating Climate Change through Food and Land Use, by Sara J. Scherr and Sajal Sthapit.
The first step is simply realizing the magnitude of agricultural or forestry-based contribution to emissions and, potentially, to absorption. Amidst the talk of carbon-scrubbers, Gehry-esque solar plants plunked down in deserts, tidal turbines, hybrid cars, and maglev trains, land is often sidetracked.
Oddly. For example, "Indonesia emits 3 billion tons of carbon dioxide equivalent annually, or about half the yearly emissions of the United States," through forest fires, illegal logging, and deforestation for the creation of palm-oil plantations.
Carbon dioxide and other greenhouse gases also seep into the atmosphere as the secondary effects of land-use changes. Exposed soil erodes more easily, and oxidizes more readily, releasing carbon dioxide into the atmosphere, while nitrogen fertilizers cause soil to emit nitrous oxide, an enormously potent greenhouse gas. The gist is that land-use change is a big problem—close to a third of the problem.
But land use can also be a big solution, even though its extent is often vastly under-appreciated.
One strategy involves pushing the carbon back where it belongs, by enriching soil carbon. As the report's authors write,
"Soil is the third largest carbon pool on Earth's surface. New mapping tools, such as the 2008 Global Carbon Gap Map produced by the United Nations Food and Agriculture Organization, can identify areas where soil carbon storage is greatest, as well as areas with the physical potential for billions of tons of additional carbon to be stored in degraded soils."
Such techniques consist of composting, green manure—growing crops during fallow periods and plowing them back into the land, thereby adding their carbon to the soil—using nitrogen-fixing cover crops, intercropping, and using livestock manure; the mainstays of organic farming. The authors cite a Rodale Institute study finding that such methods could sequester 4 percent of U.S. greenhouse gas emissions if the 65 million hectares in the United States planted with corn and soybeans were converted to organic methods.
They also mention the promising prospects of no-till farming and biochar—no cure-all but a potentially amazing technology worth serious investigation.
Another strategy is transitioning to perennial agriculture, growing crops that do not need to be replanted every year. Such crops grow deep root systems, keeping "living biomass" in the soil, and doing away with annual tilling that exposes soil carbon to oxidization and atmospheric diffusion. Already, numerous alternatives exist for many of the most commonly-grown cereal crops, some of them beginning to approach the productiveness of annual varieties.
Agro-forestry operates on the same principle, as with the "Billion Trees Campaign," launched in 2006:
"Within a year and a half, the program had shattered initial expectations and mobilized the planting of 2 billion trees in more than 150 countries. Half the plantings occurred in Africa, with 700 million in Ethiopia alone."
The third strategy is transitioning to a more climate-friendly livestock system. The most climate friendly move is to simply eat less meat, as scientists have long recognized. Palliative measures include rotational grazing systems, allowing vegetation to re-grow after animals graze it, adding nutritional supplements to reduce methane emissions, and processing manure into bio-gas rather than letting it decompose out in the open.
Another strategy is conserving or restoring natural habitats. The report notes that in many areas,
"the challenge is to develop incentives for conservation for the key stakeholders. Several approaches are being used. One is to raise the economic value of standing forests or grasslands by improving markets for sustainably harvested, high-value products from those areas or by paying land managers directly for their conservation value," and paying off third-world countries for keeping their natural habitats intact, as Ecuador's Rafael Correa has proposed for the Yasuni.
Another approach is to certify products as not having caused deforestation during their production. That includes securing local rights, "so that local people have an incentive to manage these resources sustainably."
The fifth strategy they outline is restoring already-ravaged areas. In water-sheds, this means restoring vegetative cover to as many areas as possible, which does not mean preventing the land from being actively used. As they write,
"Poor vegetative cover limits the capacity to retain rainfall in the system or to filter water flowing into streams and lakes—therefore accelerating soil loss. From a climate perspective, lands stripped of vegetation have lost the potential to store carbon."
India and China have initiated major efforts to re-vegetate their watersheds. In Niger, a more general effort has reversed desertification and increased green cover by 10 or 20 times. Perhaps 25 percent of the country's farmers have been involved in the restoration efforts.
The authors cite IPCC figures suggesting that at a carbon cost of 20 dollars per ton of carbon/equivalent, "1.5–1.6 billion tons can be sequestered annually from better agronomic, grazing, and soil management practices, and 5.8 billion in the forestry sector." At 100 dollars per ton, the numbers are 4.0 to 4.3 billion from agriculture, and 13.8 billion from the forestry sector. The technical capabilities are close to double that, suggesting that maybe other routes than bribing people not to pollute may be in order.
Can all this work?
The report parries three common objections: the reductions' permanency, whether "climate benefits [will] actually be greater than those expected in the baseline conditions—that is, will they be additional?" and whether the offsets will simply lead to increased emissions elsewhere.
Permanence relates to the fact that carbon stores in vegetation and soil is easily released, and thus there's less incentive to adopt practices that store it in the first place.
"Land use is inherently dynamic in response to both ecological processes and economic incentives, so any system that incorporates farming and land use action must allow for site-level changes. One approach commonly used in forestry projects is to calculate tree growth and harvest regimes, and to recognize only the net carbon sequestration."
This often-enough involves shifting whole watersheds or zones into being emissions-negative. In terms of additionality, this means making sure that the carbon wouldn't have been sequestered anyway, a somewhat thorny issue. As for whether the practices will simply lead to increased emissions elsewhere, the solution is
"Implementation at a large scale, spatially. Here, monitoring and financial support take into account the net change in emissions across the entire area or market. This is the motivation behind the requirement that countries develop national baselines to become eligible for large payments for REDD activities." Some caution that this can cede local autonomy over natural resources third parties.
The authors move on to implementation, citing several obstacles, including the difficulties of tying together numerous small-scale projects into larger initiatives. They specifically cite third-world endeavors as being notably successful—India, China, Niger, Tanzania, and add that small-scale discussions shouldn't be seen as a stumbling block but rather as a heartening increase in democratic control.
They add that the food industries and national governments should be seen as two important contributors to the overall project: food industries' contributions could include labeling products so as to indicate their climate cost, providing an incentive for removing carbon from the supply-chain—what they call "consumer and buyer awareness." Again, one can register qualms with reducing peoples' ability to impact the spoliation of the global commons to their consumer preferences.
But then the authors move on to the issue of "co-benefits," or other benefits to be derived from a concerted effort to reduce land-use-based emissions. They note that many efforts to reduce emissions go hand-in-hand with efforts to promote sustainable development, cleaner air and water, and more productive agriculture.
They end with a declaration of six principles:
1. Include the full range of terrestrial emission reduction, storage, and sequestration options in climate policy and investment.
2. Incorporate farming and land use investments in cap-and trade systems.
3. Link terrestrial climate mitigation with adaptation, rural development, and conservation strategies.
4. Encourage large, area-based programs.
5. Encourage voluntary markets for greenhouse gas emission offsets from agriculture and land use.
6. Mobilize a worldwide, networked movement for climate friendly food, forest, and other land-based production.
There are some problems with these suggestions: cap-and-trade, for example, is by no means a panacea, and pretty easy to undermine if the current negotiations are any indication. But for a good overview of the current state of the politics and science of agriculture's and land's ability to reduce emissions, the report is a good place to go.