Itissaidthatfarmersorpeasants,especiallythoseindevelopi...

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It is said that farmers or peasants,especially those in developing countries,are often criticized for cutting down a new study suggests that many farmers recognize the value of keeping trees.

Researchers using satellite images found at least ten percent trees cover on more than one billion hectares of farmland._36_ier estimates were much lower but authors of the new study say it may still underestimate the true extent worldwide.

The study found the most trees cover in South America._37_h Africa and West Asia have the least.

The study found that climate conditions alone could not explain the amount of trees cover in different areas. _38_e are areas with few trees but also few people,and areas with many trees and many findings suggest that things like land rights,markets or government policies can influence tree planting and protection.

Dennis Garrity heads the World Agroforestry Center._39_ problem,he says,is that policy makers and planners have been slow to recognize this and to support such efforts.

The satellite images may not show what the farmers are using the trees for,but trees provide nuts,fruit,wood and other products._40_ under drought (乾旱) conditions,trees can often provide food and a way to earn money until the next growing season.

Some trees act as natural take nitrogen (氮氣) out of the air and put it in the ntists at the Center say the use of fertilizer trees can reduce the need for chemical nitrogen by up to s also capture carbon dioxide,a gas linked to climate change.

could the size of nearby populations,meaning people and trees can live together.

says farmers are acting on their own to protect and plant trees.

st all of it is covered by trees.

also help prevent soil loss and protect water supplies.

devotes most of his time to making people realize its importance.

is nearly half of the farmland in the world.

comes Africa south of the Sahara,followed by Southeast Asia.

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