Thanks to protracted temblors in the US (and some other English-speaking nations) over the role of fossil fuels in generating climate change, many of us sometimes forget that agriculture, deforestation, and land use change (AFOLU, for short) also emit a large proportion of greenhouse gases.
Those with a rough idea of how the emissions pie divides often point to deforestation as the greatest of these three climate threats. It certainly used to be, but in an article based on 22 years of global warming data, Francesco Tubiello and colleagues from Italy, Japan, and Great Britain recently challenged that assumption.
The authors refined the global emission updates provided in the UN’s IPCC fifth assessment summary (2014) to include all three available AFOLU datasets (instead of the single dataset IPCC finally used). They converted carbon dioxide, methane, and nitrous oxide figures into carbon dioxide equivalents for ease of comparison. Their article was published online in Global Change Biology earlier this month. Rosamund Pearce of CarbonBrief prepared this excellent infographic.
Recranking the numbers, the researchers first found that AFOLU emissions to the anthropogenic total have declined over time. Their annual value equalled 21.2 ± 1.5% in 2010, versus the 24% presented by the IPCC. Although emissions of the AFOLU sector as a whole are dropping, emissions from agriculture are still headed in the wrong direction.
Farming continues to use large amounts of both freshwater and fossil fuels. Agriculture (crop and livestock production) had a larger slice of AFOLU in 2010, contributing 11.2 ± 0.4% of total GHG emissions, compared to 10.0 ± 1.2% produced by the land use sector (including deforestation). Since the 1990s, deforestation has fallen from 12% of total anthropogenic emissions to only 8% by the new calculation.
Determined efforts such as reforestation and the 10-year reducing emissions from deforestation and forest degradation initiative are responsible for the drop. Tubiello and colleagues suggest that these results can further inform the current climate policy debate on land use. Along the same lines as REDD+, options for mitigation in agriculture merit more resources than we are currently devoting, they say.
The growing movement for Climate Smart Agriculture seems to have relevance here. It seeks to reverse the climate-harmful effects of farming without relying on carbon offsets. Its advocates seek to increase crop yields, store more carbon in the soil, and promote climate resilience, maximizing farm output in a changing climate and thus achieving both food security and climate change objectives. CSA proponents specify different regional and/or national emphases according to each area’s current level of agricultural development.
“Developed countries… may focus on reducing energy inputs and emissions, and look for suitable opportunities for biofuel production. Others may look at opportunities for carbon trading from agricultural production, while the least developed countries are likely to be predominantly focussed on adapting their agricultural systems to meet the challenges posed by a changing climate.”
As David Howlett of Leeds University’s Africa College says, CSA can help reduce emissions and sequester carbon, reduce pressure on forests, maintain ecosystem services and biodiversity, and produce food, fiber, and fuel crops that the world needs.
It may be instructive here to take a look at the potential post-2020 contributions of the AFOLU sector from the top eight nations in terms of emissions, production, or mitigation potential from the land. Below, we summarize characterizations coming from Halfway There, the January 2015 Union of Concerned Scientists publication by Doug Boucher and Kalifi Ferretti-Gallon that we reviewed several weeks ago.
First, the post-2020 climate mitigation potentials:
Second, brief descriptions by nation:
The US potential for reducing land-sector emissions is promising. It includes demand-side strategies like reducing beef consumption (now at levels with negative consequences for public health), and reducing food waste, particularly of high-emissions foods. On the supply side, possibilities include reducing N2O emissions from overfertilization and preventing deforestation and depletion of agricultural soils. [Deforestation has been particularly severe in the southern United States.]
Indonesia is now the largest forest-sector emitter in the world, both from deforestation and the clearing of peat swamps. Reducing these emissions and restoring forests and peat lands offer major opportunities for mitigation.
China boasts a net sink in its forest sector due to large-scale reforestation efforts in recent decades. However, the country’s agriculture is a major emitter, with N2O from overfertilization and methane from rice representing important opportunities.
India’s emissions profile is distinctive: it has net sequestration in its forest sector due to past reforestation efforts, and the country’s population consumes few high-emissions foods. As a result, India’s agricultural mitigation potential is nearly all on the production (supply) side. This includes opportunities to reduce emissions of N2O from overfertilization and methane from rice.
Brazil is internationally recognized for having reduced Amazon deforestation by 75% over the past decade, but because of the country’s size there remain substantial opportunities from further reductions in deforestation, both in the Amazon and other biomes, as well as from reforestation. A major study by Brazilian researchers found that the cattle sector, which is not only the country’s largest source of direct global warming emissions (such as methane) but also the predominant driver of deforestation, is where Brazil has the greatest mitigation potential.
The EU is important to global agriculture as a producer, consumer, importer, and exporter, and it consumes high levels of emissions-intensive foods such as beef. Demand-side approaches to shifting dietary patterns and reducing food waste offer substantial opportunities for reduction.
Mexico has greatly reduced its loss of primary forests in recent years and has the potential to become a net sink through reforestation and restoration of other ecosystems. There are opportunities in agriculture as well, both on the production side and by slowing the growth of beef consumption.
Democratic Republic Of The Congo
Although it is the largest country in Africa, the DRC has relatively low levels of deforestation, ruminant emissions, and agriculture-linked soil emissions. Its major potential is in the reduction of forest and savanna emissions associated with selective logging and fires, an area in which other central African nations have made considerable progress in recent years. The median estimate of the DRC’s potential is 0.02 Gt CO2/year both in 2020 and 2030.
Finally, relative mitigation potentials by AFOLU subsector:
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