23.12.2020 |

Food system changes needed to reduce biodiversity loss, study finds

Demand for agricultural land drives deforestation (Photo: CC0)

What we eat and how it is produced will need to change dramatically to prevent widespread biodiversity loss, according to new research published in “Nature Sustainability” on 21 December. If current agricultural trends continue, between 2 and 10 million square kilometres of new agricultural land could be cleared by 2050, mainly at the expense of natural habitats. An international research team has now projected that almost 90% of species could lose part of their habitats. “We estimated how agricultural expansion to feed an increasingly wealthy global population is likely to affect about 20,000 species of mammals, birds, and amphibians,” explains lead author Dr David Williams from the University of Leeds. “Nearly 1,300 species are likely to lose at least a quarter of their remaining habitat, and hundreds could lose at least half. This makes them far more likely to go extinct,” he warned. But there is hope: Future biodiversity losses could be reduced by adopting healthier diets, cutting down on food loss and waste, increasing crop yields and implementing global land-use planning. “We need to alter both our diets and food production methods,” says Williams.

The researchers developed a model to forecast where agricultural land is likely to expand based on observed historical changes in agricultural land cover from 2001 to 2013 and data on likely determinants of land-cover change, such as the suitability of an area for agricultural production, proximity to other farmland or market access. By linking this model to country-level estimates of agricultural land demand between 2010 and 2050, based on population sizes, per capita GDP and agricultural yields, they were able to project where, and by how much, agricultural land was likely to change in the future. The scientists then overlaid these forecasts with habitat maps for almost 20,000 species of amphibians, birds and mammals. They used a very fine spatial resolution of 1.5 × 1.5 km which allowed them to determine exactly which species and landscapes are likely to be threatened and they looked at whether those specific species can survive in farmland or not. This allowed them to calculate the proportion of habitat each species would lose from 2010 to 2050.

The researchers found that under business-as-usual, global cropland could increase by 26% or 3.35 million km2 from 2010 to 2050. Large increases are projected to occur throughout sub-Saharan Africa, South and Southeast Asia (particularly Bangladesh, Pakistan, and southern Malaysia) and in northern Argentina and much of Central America. These increases are driven by “income-dependent transitions towards diets that contain more calories and larger quantities of animal-based foods, combined with high levels of projected population growth and low crop yields that are projected to increase slowly, particularly in sub-Saharan Africa,” the authors write. The scientist projected that, if current trajectories continue, 87.7% of species (17,409 species) would lose some habitat by 2050, while 6.3% would have no change in habitat area and 6.0% would see an increase because they can live on agricultural land. However, the authors highlight that mean values conceal the severity of projected habitat losses for many species. By 2050, 1,280 species could lose at least 25% of their remaining habitat area and could be at increased risk of global extinction in the coming decades. More alarmingly, 347 species were projected to lose at least 50% of their remaining habitat, 96 at least 75%, and 33 at least 90%. Many of the species that are likely to be most affected are not listed as threatened with extinction, and so are unlikely to be currently targeted by conservationists.

The scientists highlight that “proactive policies targeting how, where, and what food is produced could reduce these threats, with a combination of approaches potentially preventing almost all these losses while contributing to healthier human diets.” To investigate the potential of such proactive approaches, they developed a scenario that implemented four changes to food systems: closing crop yield gaps globally, a global transition to healthier diets, halving food loss and waste, and global agricultural land-use planning to avoid competition between food production and habitat protection. They examined both a ‘combined approach’ scenario and the impacts of each approach individually. The simultaneous adoption of all four scenarios would reduce global land demand by 2050 by nearly 3.4 million km2 relative to 2010, and by 6.7 million km2 relative to business as usual. Under the combined approach, all regions would just see mean habitat losses of 1% or less by 2050 – only 33 species were projected to lose more than 25% of their habitat, compared with 1,280 under business-as-usual.

The impacts of individual approaches varied regionally. For example, increasing yields would bring huge benefits in North Africa, West Asia, and sub-Saharan Africa, where large yield gaps remain, but the scientists also warn that increasing yields often has negative consequences for species within agricultural lands. In contrast, yield increases would have a small impact on biodiversity in North America, where yields are already close to their maximum. Transitioning to healthier diets and reducing food waste were projected to have considerable benefits particularly in wealthier regions with high per capita consumption of both calories and animal-based foods. However, shifting to healthier diets is less likely to have a large benefit in regions where meat consumption is low and food insecurity is high. Global land-use planning had smaller impacts, with 1,026 species still projected to lose at least 25% of their 2010 habitat. Sub-Saharan Africa would benefit most from this measure. The scientists say that looking at the impact of each approach individually can help policy makers and conservationist to identify which changes are likely to have the largest benefit in their country or region. “Importantly, we need to do all of these things,” said Dr Michael Clark from the University of Oxford, who is also a lead author on the paper. “No one approach is sufficient on its own.” The authors stress that focusing on conventional conservation actions, such as establishing new protected areas or legislation for threatened species, is not enough. The underlying drivers of agricultural expansion need to be addressed. “The good news is that if we make ambitious changes to the food system, then we can prevent almost all these habitat losses,” Clark added. The authors conclude: “These proactive efforts to change how we produce and consume food will be a major challenge, but one which cannot be avoided if we are to safeguard species for future generations.” (ab)

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