Science

Published on August 27th, 2009 | by Steve Savage

2

Farms Around the World Have More Trees than Expected

Trees along a farm road in New South Wales

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The World Agroforestry Centre has recently released a paper titled Trees on Farm: Analysis of Global Extent and Geographical Patterns of Agroforestry.” The researchers used five global geodata sets to estimate the percent tree cover on 22 million square kilometers of agricultural land around the world.  They were surprised to find that nearly half of that land had 10% or more tree cover (which is considered “significant” from an agroforestry point of view).  The area involved is vast – as large as the Amazon basin.

Even for North America, the percentages were surprisingly high (39% over 10% cover, 17% over 30%).  Values in Europe were similar. The highest levels are in central America (98% above 10% cover), South America (81%), and Southeast Asia (82%).  Overall, the lowest tree cover is in the most arid areas, but even there >20% of the farmland has 10% tree cover.

What Trees Do for a Farm

The trees serve many functions.  Some are actually crops.  Some are being grown for wood.  Some are windbreaks that protect crops from damage.  Some are to prevent erosion.  Some help define boundaries. Many are just there for shade or aesthetics.  Farmers, like everyone, enjoy having trees around.

In any case, these millions of trees are sequestering carbon in the soil and providing habitat for a variety of creatures.  They can capture pollutants that might otherwise move into surface or ground waters.  They are removing pollutants from the air and providing cooling.

There are reasons farmers might not want too many trees.  They can compete for water in dry areas.  They can be a roosting place for birds that then come in great numbers and damage crops.  Tree roots can damage drain tile or irrigation lines or interfere with roads.  Still, it seems that the pluses outweigh the minuses on many farms.

This is a nice of example of a sustainable farming practice that has been going on spontaneously without any pressure from we urbanites. Good for the farmers!

Image of trees at a farm in New South Wales by stage88



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About the Author

Born in Denver, now living near San Diego. Agricultural scientist for 30+ years with a Ph.D. in Plant Pathology. Have worked for Colorado State University, DuPont and Mycogen and for the last 13 years consulting for all sorts or companies, universities and grower groups. Experience in biological control, natural products, synthetic chemicals, genetics, GMOs and agronomic practices. Have given multiple invited talks on the interaction between agriculture and climate change (both ways)



  • http://www.greenwaycommunique.com Nathan Schock

    This study isn’t surprising to those of us who live in the Midwest (otherwise known as flyover country). We call the trees “shelterbelts” and have considered them an essential part of farming for the reasons you laid out above.

  • http://appliedmythology.blogspot.com Steve Savage

    Nathan, probably too late for you to notice, but you make a great point. Farmers are mostly responsible stewards of the land.

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