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Slash and burn farming

Wednesday 6 January 2010
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Unsustainable farming methods continue to endanger planetary soils. Giles Crosse plants some ideas for a more productive relationship.

“Conservation agriculture is an alternative to slash and burn crop production methods that were used successfully for millennia,” says Theo Dillaha, Program Director of the SANREM CRSP and Professor of Biological Systems Engineering at Virginia Tech.

“The basic principle of slash and burn agriculture is to alternate lands between crop production and native vegetation and forests. During crop production without fertiliser additions and good soil management practices, soil quality and crop yields decline over time.”

“When crop yields decline to unacceptable levels, the fields are abandoned, and regrowth of native plants restores soil quality over time. Once the soil quality is restored, the native vegetation can be cut and burned to release nutrients back into the soil for crops.”

Dillaha explains this system worked well when there was ample time for native vegetation regrowth, typically five or more years for each year of cropping. But population increases and food needs have decreased the forest period of the cycle so much that slash and burn is no longer effective.

Alternatively then, conservation agriculture is a proven technique seeking to maintain and restore soil quality. And doing so is vital. As is so often the case, developing world farmers are often the most tempted to use short term unsustainable methods. But destroying the land’s fertility only reduces production potential, speeding migration, conflict and associated impacts.

Safer soils

Dillaha identifies three key drivers for healthy lands: maintaining year round soil cover, with residue from previous crops or a cover crop, minimising soil disturbance by tilling, and rotating crops to improve soil health and discourage agricultural pests.

But there are other crucial issues. Agricultural expansion is among the greatest contributors to deforestation. Such expansion is sped by slash and burn, in turn sped by poor food prices or rising populations. This quickens world poverty, while unemployment speeds further the unsustainable rush to strip land for a quick buck.

“In seeking solutions to deforestation or forest degradation we often make the mistake of treating environmental issues separately from social and economic issues,” says Dr. Yemi Katerere, Head of the UN-REDD Programme. REDD wants to create a financial value for the carbon stored in forests, offering incentives for developing countries to reduce emissions from forested lands and invest in low carbon paths to sustainable development.

“These are in fact interrelated,” Katerere explains. “We need to understand the underlying causes of these problems in order to find sustainable solutions. The underlying causes of deforestation vary from country to country, but there are some common threads.”

“The greatest threat to forests is the expansion of agriculture, crops and livestock, small and industrial scale. Often peoples’ rights to resources are poorly understood, often they are inherited or embedded in traditional culture and are in conflict with formal legislation of the state.”

“Frequently this results in incentives to assert rights to land by forest clearance or to forest resources by premature harvesting. Thus clarification of rights, responsibilities and entitlements among instances of the state, communities and individuals is critical to reversing drivers of deforestation and forest degradation.” Such clearance only rapes more nutrients from soils, denying future generations.

Grounds for hope

To truly alter damaging land use practices, understanding and respecting how drivers force people to abuse their resources is vital. “Poverty and lack of non farm employment opportunities are also underlying causes of deforestation,” reveals Katerere.

“The economies of most developing countries are dependent on natural resource exports and hence can fall victim to the vagrancies of globalised trade and pricing. The lack of off farm employment opportunities forces farmers to remain on the land even when such an option is not viable.”

“Inequitable land distribution and unclear land tenure are also underlying causes of deforestation. Lack of incentives for people to manage forests for the ecosystem services they uniquely provide is also an underlying cause.”

Katerere criticises the globalised trade in forest and forest based products, which often has impacts on local people, for example beef and timber in the Amazon, in a way that many national governments fail to understand and respond to.

“To move towards sustainable agriculture requires that countries begin to look at a new generation of policies, that can transform their economies towards a desired path of economic development that is sustainable.” Katerere reveals.

“This begins by acknowledging the nexus between sectors, by addressing tenure rights and rewarding communities and local farmers for practices that are environmentally sustainable. Studies show that where local farmers and communities have entitlement and benefit from the management of their natural resources, they champion the custodianship of their forests and land.”

“Additionally much can be done in terms of shifting production to higher value crops or livestock, providing improved technology - better access to markets including the removal of tariff and non tariff barriers and better integration of value chains.”

“This would help to improve productivity and income from existing plots. Finally improving women’s rights and building on their roles as stewards of the land would be important.”

Developing resources

Katerere reckons developing country governments also need to develop strategies that help move their countries towards low carbon economies. “For forest rich countries, it is hoped that revenues earned from reducing carbon emissions from deforestation and forest degradation can be invested in transitioning to a low carbon economy.”

“It should however be pointed out that slash and burn agriculture is not intrinsically unsustainable, in fact given adequate forest areas and sufficiently long cycles it has sustained human life in most rainforest areas for thousands of years with no obvious adverse impact on the forests.”

The truth is, only in recent times has a combination of growing populations, shrinking forest areas, production for markets and mechanisation resulted in unsustainable cycles. This seems paralleled by the increasing demand for profit and lack of long term thinking so visible among today’s economic models.

“As population densities increase, so does the pressure on the land and the shorter the fallow periods,” explains Katerere. “Farmers are forced to clear new forests or return to old fields before the forest has adequately regenerated. Besides resulting in forest and biodiversity loss, reduced soil fertility and at times soil erosion, this also contributes to global carbon emissions.”

“Alternatives to slash and burn include agroforestry practices that integrate trees into the farming landscape. These trees provide multiple benefits such as nitrogen fixing, mulching, fodder, fuel wood, food and medicines. On slopes, farmers can also prepare terraces to reduce soil erosion.”

“Other alternatives include permanent sedentary agriculture where soils are suitable and adverse environmental impacts can be tolerated. In many forest areas the best alternative may be to resort to non or less destructive uses of forests. For instance many natural forests around the world support large populations who harvest fruit, leaves, bark, gums and resins leaving the forest structure more or less intact.”

Mitigation and management

As with so many planetary issues, the drivers behind land abuse relate to the race for cash, resources and the battle to beat neighbours and countries to the prize. Changing this will require step changes across planetary resource sharing and political and economic point scoring. This will take time.

“One thing that policy makers need to come to terms with is that there needs to be a shift away from a dichotomist approach to national development that over invests in urban areas at the expense of rural areas.” concludes Katerere.

“Secondly, the notion that all rural inhabitants should be farmers tilling the land also needs to change. There has to be a comprehensive and integrated national economic development vision and strategy that promotes sustainable development by reducing dependence on natural resources, especially those that are climate sensitive.”

“In Malawi for instance, agricultural plots have been getting smaller and in many parts of the country have become too small to meet the subsistence needs of a family. What we really want to do is find a way for REDD to be the catalyst to bring about the transformation of rural economies, and technology will play an increasingly vital role in improving agricultural productivity.”

Sadly, it’s unlikely the solution will be found in technology alone. The real scale of the challenge is only now being appreciated.


Sanrem Crsp Policy Brief: Vegetable agroforestry in the Philippines. The policy environment and incentives for small landowners

Sanrem Crsp Research Brief: Lowland Irrigation Practices Benefit Upland Farms

Rotational Grazing for Soil Carbon Sequestration

Understanding Alternatives to Forest Use in Malawi

USAID Agriculture Strategy Linking Producers to Markets

USAID: Agricultural Biotechnology for Development

Improving Lives through Agricultural Science and Technology

UN Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation in Developing Countries


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