Ant study shows better biodiversity conservation needed on farmland in the tropics

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A new study, led by CABI scientist Dr Elizabeth Finch, is the first to investigate the impacts of shifting cultivation on ant communities across the entire degradation gradient, highlighting the critical importance of conservation existing closed canopy forests.

Shifting agriculture, more commonly known as slash-and-burn agriculture, is a subsistence farming method prevalent in the tropics that intensifies and expands to meet the demands of a growing human population. In Madagascar, for example, fallow periods fell from 8 to 15 years to 3 to 5 years in three decades, leading to faster land degradation.

The research, conducted while Dr. Finch was completing his doctorate. at the School of Biological Sciences, Queen’s University Belfast and now published in the journal Biological conservation, reveals that degradation due to shifting cultivation leads to a reduction in the diversity of native ant species and an increase in the diversity of introduced ant species. There were also correlated community composition changes in native and introduced species.

Introduced ant species are often favored in disturbed habitats and can reduce the diversity and distribution of native ant species. They therefore represent a confounding factor when considering the effects of habitat degradation. The study results, however, found little statistical evidence that introduced ant species had a negative impact on native ant species. This suggests that patterns in native ant communities were solely driven by habitat degradation caused by shifting cultivation.

Dr Finch said: “Ants, in soil structuring, seed dispersal, decomposition, pollination and nutrient recycling, play an important ecological role in tropical ecosystems and as such it is important to understand how they are affected by land use change to assess sustainability.”

Scientists, including those from the Madagascar Biodiversity Centre, the University of Bangor, Wales, University College Dublin and the California Academy of Sciences, have found that in general predatory species were most likely to be negatively affected by swarming, while omnivorous species were most affected. likely to benefit from this form of agriculture.

Dr Finch added: “We found that closed-canopy forests had the highest diversity of ant species and were compositionally unique. This highlights the importance of their conservation.

“However, we also found that less degraded burnt habitats harbored unique and native ant species. We recommend that if these habitats are used sustainably, with long fallow periods to avoid the spiral of degradation, these could still play an important role in conserving biodiversity in burnt landscapes across the tropics.

“We need to find a way to increase crop yields to relieve the pressure enough so that longer and more sustainable fallows can be achieved. Slash-and-burn systems have demonstrated the ability to maintain and even increase carbon stocks for curbing climate change by halting deforestation, could therefore potentially close the economic gap that is essential to ensure the sustainable implementation of such measures.”

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More information:
Elizabeth A. Finch et al, The effect of shifting cultivation on ant communities in Madagascar, Biological conservation (2021). DOI: 10.1016/j.biocon.2021.109400

Provided by CABI

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Amalia H. Mercado