BONN (Reuters) - A new focus on the impact of farming on climate change could both curb carbon emissions and prod efforts to boost yields and rural incomes in developing countries, delegates told a U.N. climate conference.
But curbing greenhouse gases from farms also means confronting complex tradeoffs, especially to try and feed an extra 3 billion people by 2050 while encroaching less on forests, burning of which stokes carbon emissions.
In addition, new incentives to curb greenhouse gases from farms such as carbon offsetting under discussion in the United States, in the U.N. talks and at the World Bank may be inappropriate and must favour smallholders, say campaigners.
"Agriculture is now mentioned," said Gerald Nelson at the International Food Policy Research Institute.
"That's a good sign but it's still very limited," said Nelson, referring to draft texts for a new treaty, which refer to high-carbon, organic soils as a possible store of the greenhouse gas carbon dioxide.
The 181-nation Bonn meeting is the latest round meant to help seal agreement in December in Copenhagen on a new climate pact to replace the Kyoto Protocol.
Africa has lower agricultural yields than farms in Asia, Europe and America. Climate-friendly practices boost fertility, especially where farming has exhausted the land.
Globally, agriculture accounts for about 14 percent of greenhouse gas emissions. But in some countries the figure is far higher.
In Uruguay, for example, farming is responsible for about four-fifths of national emissions, especially as a result of herds of 12 million cattle and 11 million sheep which produce the powerful greenhouse gas methane.
Cattle add to climate change both by belching the greenhouse gas methane and by requiring more land per calorie produced than food crops, thereby stoking forest loss.
Methane can be trapped, or cut using better feeds and livestock breeds. But farming can have a far bigger effect to curb climate change by storing carbon in the soil.
That could trap 1-2 billion tonnes of carbon per year, compared to annual emissions from burning fossil fuels of about 8.5 billion tonnes, analysts say.
A key challenge, however, is that many practices which store more carbon and cut emissions of power greenhouse gases from fertiliser, such as organic agriculture, can be lower yielding than intensive alternatives.
But a drive for freer trade has cut food reserves, while new technologies have increased farmer indebtedness.
"We ignore these connections at our peril," said Jim Harkness from the U.S.-based Institute for Agriculture and Trade Policy. Some green groups oppose one possible solution -- to use more genetically-modified crops.
Climate-friendly measures can boost soil fertility and aid water retention. In Kenya farmers are planting trees among crops to boost tired soils, said Pete Smith, lead author for farming on the U.N.'s Intergovernmental Panel on Climate Change.
"They cut off the leaves from fast-growing trees, feed them to goats, so their productivity goes up, they then take the manure and put it back into the soil which improves the soil fertility." The trees store carbon in their trunks and soil.
Another practice is where farmers plough the soil less to keep high-carbon organic matter underground. That can also aid drought resistance, because not ploughing keeps leaves on the ground which trap moisture.
"Increasing carbon sequestration is only one reason to be good to our soil but a very good one," said Doreen Stabinsky, agriculture campaigner at Greenpeace, on the sidelines in Bonn.
But not tilling the soil can actually cut stored carbon if the soil becomes so compacted that plants can't grow.
That's an example of a nuance, alongside difficulties of measuring soil carbon, and the fact it may stay be stored only temporarily, which some campaigners fear makes the sector unsuitable for inclusion in carbon offsetting markets.
Carbon offsetting allows rich countries to continue to build coal plants, for example, provided they fund emissions cuts in developing countries.
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