Green Forests?

This post contributed by Heather Kirk, a post-doctoral researcher at the Institute of Agricultural Sciences in Zurich, Switzerland When a 9.0 magnitude earthquake caused a series of nuclear accidents in Japan back in March of this year, there was nervousness in North America that nuclear fallout could blow across the Pacific Ocean to reach coastal cities in Canada and the US.  While those fears were largely unfounded according to health officials, West Coast residents have certainly received air-borne “gifts” from Asian countries in the past. Every year, China and a number of other Asian countries are the source of massive dust storms that spread over large portions of the Asian continent, and sometimes even cross the Pacific.  These storms have intensified over the past century as a result of deforestation, overgrazing, and poor water management.  In 2010, East Asia experienced particularly bad droughts that led to food shortages and massive dust storms that lasted for days and traveled thousands of kilometers. In order to address these storms and their causes, China has implemented a tree-planting policy that aims to reduce erosion and evaporation of precious water resources, while providing new sources of economic growth (via timber and tree-fruit production).  The most internationally publicized of these initiatives is the “green wall of China” project, which was initiated in 1978 as part of a larger plan to stop the expansion of the Gobi desert.  The project aims to develop a green belt more than 4000 km in length along the edge of the desert. In the September 22, 2011 issue of Nature, Jianchu Xu, a senior scientist at the World Agroforestry Centre and a professor at the Chinese Academy of Sciences, comments on the detrimental effects of the widespread planting of non-native trees in China, which comprise a large portion of reforestation projects.  Most reforested areas are planted with crop species that include fruit trees, eucalyptus, and rubber, and not with native mixed forests that promote biodiversity and are better suited for providing ecosystem services such as erosion control. Additionally, new forests are being planted in areas that were not historically forested such as grasslands. In his paper, Xu states: “I would like to see China establish parallel forest-management programmes for recovery and restoration of natural forests, and for incorporating working trees into farmlands. Each should include best practices from ecosystem science; a clear definition of tree crop plantations for timber or non-timber products would clarify the separate systems”. Afforestation is an important strategy for carbon sequestration, and can play a valuable role in both ecosystem remediation and economic development.  However all forest are not created equal: some are greener than...

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Study finds more agricultural trees than we thought

Sorghum grown under acacia and palm trees in Burkina Faso. According to a new study by scientists at the World Forestry Centre in Nairobi, Kenya, we’ve underestimated that amount of trees worldwide that are grown in agricultural areas. Using satellite imagery, the scientists show at the 2nd World Congress of Agroforestry this week in Nairobi that trees cover more than 10 percent of about 10 million square kilometers of farmland — about half of the world’s farms — across North America, Asia, Europe and Africa. Agroforestry is the practice of integrating trees into agricultural landscapes. A classic example of the ways this benefits farming is shade-tree coffee plantations, where trees provide habitat for birds as well as shade for the coffee plants growing underneath. Trees on farmlands also provide ecosystem services such as fertilizing the landscape, preventing erosion and helping to filter water runoff.  Dennis Garrity, the Centre’s Director General, elaborated in a statement: The area revealed in this study is twice the size of the Amazon, and shows that farmers are protecting and planting trees spontaneously. The problem is that policymakers and planners have been slow to recognize this phenomenon and take advantage of the beneficial effect of planting trees on farms. Trees are providing farmers with everything from carbon sequestration, to nuts and fruits, to windbreaks and erosion control, to fuel for heating and timber for housing. Unless such practices are brought to scale in farming communities worldwide, we will not benefit from the full value trees can bring to livelihoods and landscapes. Additionally, agricultural landscapes that have higher biodiversity are known to export fewer pollutants into watersheds. The World Forestry Centre advocates that there should be incentives for farmers to cultivate trees that provide such valuable services, and that policy should change to reflect those incentives.  Particularly in developing countries, says the Centre, it would help farmers — especially those in developing countries — adopt various agroforestry practices more rapidly if their trees were included in international climate change mitigation schemes now under development. Read more about agroforestry at the World Agroforestry Centre’s web...

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