Slash-and-Burn Farming: A Way to Boost Forest Biodiversity

The study revealed that in sections of the rainforest where Indigenous farmers practiced slash-and-burn agriculture, creating farm patches of intermediate size—neither too small nor too large—there was a notable increase in forest plant diversity. This finding challenges the traditional perspective, previously endorsed by entities like the United Nations, which viewed slash-and-burn as a major contributor to global deforestation. Sean Downey, the lead author and associate professor of anthropology at The Ohio State University, highlighted this shift in understanding.

Sean Downey, the lead author of the study and also affiliated with Ohio State’s Sustainability Institute and Translational Data Analytics Institute, emphasized that the research offers quantitative evidence supporting the positive impacts of traditional agricultural practices on forests. He highlighted the profound understanding of forest ecology held by Indigenous communities, emphasizing that this knowledge informs practices that contribute to biodiversity enhancement and overall ecosystem improvement.

Published in the journal Communications Earth & Environment, the study involved collaboration between Ohio State researchers and local researchers, as well as active participation from community members. Focused on two Q’eqchi’ Maya villages, Crique Sarco and Graham Creek, located in the Toledo District of Belize, the study area spanned approximately 18,000 acres. Sean Downey, involved in the villages since 2005, spearheaded the research efforts.

Over 75% of the population in the two villages depend heavily on slash-and-burn agriculture, known as swidden in anthropological terms, as a primary means of sustaining their livelihoods. The cultivation of corn holds paramount importance in this agricultural practice.

Swidden farming takes place on community-owned lands, governed by local customs and norms. Residents selectively clear portions of the forest according to their requirements, employing tree burning to enrich the soil with nutrients. After cultivating the land for a few years, they allow it to revert to its natural state, moving on to a new section of the forest for farming.

Researchers employed a range of methods, including drone-based remote sensing and on-the-ground mapping, to estimate the diversity of plant species in specific areas. This information was then correlated with landscape disturbances in the primary swidden-utilized zones of both villages as part of the study.

In April 2018, the research team deployed long-range drones soaring at an altitude of 1,500 feet, equipped with a 5-band multispectral sensor to survey the designated study region. These sensors detected subtle fluctuations in the light reflected by the trees and vegetation constituting the upper canopy of the forests—referred to by scientists as spectral diversity.

Increased levels of spectral diversity, as explained by Downey, indicate a richer variety of tree and plant species. The drones, flying in close proximity to the upper canopy, utilized sensors that captured high-resolution imagery, surpassing the capabilities of satellite-based observations. This enabled the researchers to conduct a meticulous analysis of biodiversity.

Moreover, the close drone observations facilitated the identification of subtle disruptions in the forest, including those resulting from swidden agriculture. The researchers employed this data to compute a “fragmentation index” for various forest regions. Additionally, in collaboration with a local mapping team, the researchers gathered land-use history data to ascertain the duration since a specific patch of forest had been utilized for swidden agriculture.

Mature forests, characterized by the presence of large trees forming a canopy, inhibit sunlight from reaching the forest floor, impeding the growth of various plant species. Swidden agriculture, in contrast, involves clearing patches of the forest, enabling sunlight to penetrate and facilitating the establishment and growth of diverse plant species. This process contributes to heightened diversity within the forest, a positive outcome.

Downey emphasized that this natural phenomenon occurs organically through events like lightning strikes, hurricanes, and storms, which create openings in forested areas. Indigenous farmers are deliberately utilizing similar processes, strategically crafting patches of just the right size to optimize species diversity.

According to Downey, the key lies in the intermediate-sized patches. In mature forests, rare species serving as seed banks are naturally scarce. If the cleared patches are too small, it hinders the growth of these rare plants. Conversely, if the patches are excessively large, it could eliminate the seed bank, preventing the resurgence of rare species in the area.

Achieving the optimal spatial scale for clearings is crucial to effectively enhance biodiversity, according to Downey. The research indicates that local farmers engaged in swidden agriculture typically demonstrate a keen understanding of this spatial balance, ensuring that the size of the clearings is precisely calibrated to promote increased biodiversity in the ecosystem.

In light of the global emphasis on Indigenous agriculture concerning climate change, Downey highlighted the significance of the study’s findings. The evidence presented underscores the positive impact of swidden agriculture, contributing valuable insights at a time when the international community is particularly attentive to the role of Indigenous agricultural practices in addressing climate-related challenges.

The United Nations climate summit, COP28, commenced on November 28 in the United Arab Emirates and includes an “Indigenous Peoples Dialogue” session scheduled for December 5. In the session summary, the UN emphasizes that Indigenous peoples play a key role in safeguarding 80% of Earth’s biodiversity.

Downey’s research implies that the imposition of top-down regulations on swidden agriculture by national and international entities may not be the most effective approach. Instead, climate change programs should be open to supporting practices and institutions that, though seemingly unrelated to conservation, hold critical significance for Indigenous cultures and livelihoods.

Downey asserts that the research illustrates how Indigenous communities, guided by their customary practices and cultural norms, have the capacity to sustain an intermediate level of disturbance in forests. This level of disturbance is shown to not only support biodiversity but, in some cases, even contribute to its enhancement.

Resources

1. ^{ONLINE NEWS} Grabmeier, J. & The Ohio State University. (2023, November 28). Slash-and-burn agriculture can increase forest biodiversity. Phys.org. [Phys.org]
2. ^JOURNAL Downey, S. S., Walker, M., Moschler, J., Penados, F., Peterman, W. E., Pop, J., Qin, R., Scaggs, S. A., & Song, S. (2023). An intermediate level of disturbance with customary agricultural practices increases species diversity in Maya community forests in Belize. Communications Earth & Environment, 4(1). [Communications Earth & Environment]

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