Slash-and-Burn Agriculture: Can It Be Sustainable Again?

Slash-and-burn agriculture is the practice of clearing and burning areas of vegetation to replenish the soil and grow food. Hundreds of millions of people around the world still rely on slash-and-burn agriculture to survive.

Today, however, slash-and-burn agriculture is hardly sustainable. It has led to deforestation, increased carbon emissions, and a loss of biodiversity. This article looks at the history of slash-and-burn, how it evolved, and whether it can be restored and practiced in a more sustainable way.

What Is Slash-and-Burn Agriculture?

Due to widespread use in many cultures, slash-and-burn has a host of other names, such as also shifting cultivation, swidden, and fire-fallow cultivation. In its traditional form, the practice involves clearing (or “slashing”) small forest areas, then burning the remaining vegetation. This returns carbon and other nutrients stored in the plant material to the soil.

The newly rich soil is planted for two to three years until the soil is exhausted. A fallow period follows, allowing plant life to regrow and soil nutrients to regenerate—and so the cycle continues, while farmers move on to new areas to cultivate.

For millennia, this has been a form of agroforestry practiced long before the words “permaculture” and “regenerative agriculture” were invented.

Benefits and Practices of Slash-and-Burn

Slash-and-burn agriculture has been called the oldest farming system in the world, practiced for at least the past 7,000 years. It has been more common than the intensive agriculture that we associate with the so-called “Agricultural Revolution” of ancient Mesopotamia.

Slash-and-burn is one of the first forms of cultivation adopted by foragers (“hunter-gatherers”) since it was compatible with seasonal migrations between hunting grounds and cultivated settlements. Many New World staples like corn, manioc, chile peppers, squashes, sweet potatoes, and peanuts are tropical forest plants first cultivated by slash-and-burn methods.

Today, small-scale subsistence farmers primarily in the forested mountains and hills of Southeast Asia, Latin America, and Central Africa continue to farm sustainably. Tree stumps are left in place, preventing erosion and creating microbial communities which nourish the soil. Manual, no-till planting keeps the soil intact, without heavy machinery to compact the soil, break up soil aggregates, or disrupt their underground ecosystems. Traditional plants species are cultivated that are well-adapted to small‐scale disturbances, and recover quickly. Fallow periods are long enough to allow flora and fauna to regrow, sustaining the region's biodiversity. Levels of nutrients, microorganisms, and sequestered carbon in the soil also recover quickly.

As a less intensive alternative to industrial agriculture, slash-and-burn agriculture allows Indigenous people to feed themselves while maintaining their traditional cultural practices.

Environmental Consequences of Slash-and-Burn

Communities that live by slash-and-burn subsistence farming are finding their way of life threatened by industrial agriculture and the consumer demands of wealthier nations. As a result, slash-and-burn is increasingly destructive of the world's forests and a significant contributor to the dual crises of climate change and biodiversity loss.

Deforestation

Deforestation is the second-largest source of greenhouse gas (GHG) emissions, accounting for between 12% and 20% of global GHG emissions. The largest driver of deforestation is land clearing for cattle and monoculture crops like oil-seed, meant to feed international consumers. Traditional slash-and-burn agriculture feeding local populations is harder to quantify but still plays a significant part.

As slash-and-burn agriculture is currently practiced throughout much of the world, clearing old-growth forests can release 80% of their stored carbon into the atmosphere. At the same time, losses to biodiversity from slash-and-burn are comparable to those of commercial logging.

Industrial Agriculture

Since the Green Revolution of the 1950s, slash-and-burn agriculture as been seen as backwards, wasteful, and “the greatest obstacle to the immediate increase of agricultural production as well as soil and forest conservation,” as the U.N.'s Food and Agriculture Organization (FAO) stated in 1957.

Since then, international aid organizations have promoted the use of industrial fertilizers and the planting of monocultures such as palms, bananas, coffee, cassava, and other export crops rather than subsistence farming. Commercial agriculture and dependence on foreign markets have led to greater land clearing and decreased fallow periods.

The expansion of industrial agriculture has also led to land seized, often illegally, from Indigenous people. Increases in population density in forested areas driven by mining, logging, and commercial agriculture (such as soy plantations or cattle ranches) has increased the amount of land that needs to be cultivated. However, it has also decreased the total area that can be cultivated by slash-and-burn. As a result, less land is able to lie fallow for long enough periods.

Cleared land needs significant amounts of time to recover if slash-and-burn agriculture is to be sustainable. Birds and mammals can take 10 years to return to cleared land. Soil can take 15 years to recover its original conditions. Tree species can take up to 20 years to recover 80% of their original diversity.

It can also take between 10 and 20 fallow years, depending on the region, for soil carbon levels to be restored to their original state. At low population densities, fallow periods can exceed 20 years, but in the past 25 years, fallow periods have almost universally declined to just two to three years, far below sustainable lengths.

How to Improve Slash-and-Burn Agriculture

The preservation of the world's remaining forests needs to be consistent with the needs of the local population—people who are rarely included in conversations and decision-making about protecting biodiversity and mitigating climate change.

Slash-and-burn agriculture remains a central part of the lives and culture of nearly half a billion people across 64 developing countries, providing livelihoods and food security. Nearly all slash-and-burn is practiced on small farms held by Indigenous people, who today preserve 80% of the world's remaining biodiversity, according to the International Fund for Agricultural Development.

Making slash-and-burn sustainable again means supporting the world's Indigenous communities, for the dual crises of climate change and biodiversity loss can only be abated by preserving human cultural diversity. “Nature-based solutions” allow slash-and-burn farmers to extend the fallow periods that are so central to carbon sequestration and forest preservation. These solutions include

• Protecting Indigenous land from commercial encroachment,
• Prohibiting the expansion of slash-and-burn into old-growth forests,
• Supporting subsistence farmers with payments for ecosystem services like carbon farming, and
• Increasing monitoring of national forests, and other efforts such as the U.N.'s Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD+) program.

If slash-and-burn agriculture has played a key role in exacerbating climate change and biodiversity loss, it can also play a key role in the solutions. That starts with preserving the practices of people who still live off it.