Habitat-creating farms are critical for both food security and biodiversity protection. Diversified agriculture is an important supplement to forest conservation in reversing tropical biodiversity declines. Forests appear to provide greater habitat for forest-dwelling species than farms. Despite this, Stanford researchers discovered in one of the world’s longest-running studies of tropical wildlife populations that, over 18 years, smaller farms with varying crop types interspersed with patches or ribbons of forest sustain many forest-dependent bird populations in Costa Rica, even as forest populations decline.
Nicholas Hendershot and colleagues evaluated trends in distinct bird populations across three landscape types in Costa Rica: woods, diversified farms, and intense agriculture in a research published in the Proceedings of the National Academy of Sciences. The steepest losses were observed in forests, followed by intense agriculture (and the species that thrived in intensive agriculture were frequently invasive). However, on varied farms, a major fraction of forest bird species, including several of conservation concern, grew over time.
“We use birds as a proxy to track the health of ecosystems. And the birds we see now are not the same as the birds we saw 18 to 20 years ago. This paper really documents this pattern,” said Hendershot, who was a postdoctoral fellow in Stanford’s Department of Biology in the School of Humanities and Sciences (H&S), the Stanford Center for Conservation Biology (CCB), and the Stanford-based Natural Capital Project (NatCap) at the time of the research.
We use birds as a proxy to track the health of ecosystems. And the birds we see now are not the same as the birds we saw 18 to 20 years ago. This paper really documents this pattern.Hendershot
Food security at stake
While this study suggests that varied farming may be important for biodiversity, the relationship is reciprocal: biodiversity is important for food security. In this case, that means having a diversity of birds feeding on insects and pollinating crops.
“Identity appears to matter a lot for pest control and other ecosystem services provided by birds. These species are not interchangeable,” Hendershot stated.
“We require a steady stream of pollinators to service farms. Approximately three-quarters of the world’s crops require pollinators to some extent, and that 75% is our most nutritious food – think of all the vitamins and minerals packed into fruits, nuts, and veggies,” said Gretchen Daily, NatCap and CCB faculty director, Bing Professor of Environmental Science in H&S, and a senior author on the paper.
“We need a steady stream of birds, bats, and other wildlife to help control pests: they naturally suppress the vast majority.” And we must begin reintroducing flood protection, water purification, carbon storage, and a variety of other critical advantages into agricultural landscapes, well beyond what can be accomplished through protected areas alone.”
Daily also noted that, in terms of food production, diversified farms are not necessarily lower yielding than intensive agriculture. “This is a recent assumption that is being overturned,” she said.
Beyond protected areas
“I have moved away from the ‘fortress’ over time,” Hendershot explained. While protected areas remain vital around the world, they are too few and far between to supply the ecosystem services that people and the environment require to survive. Working landscapes are critical right now for protecting biodiversity and the benefits it provides. “People, including scientists, believed that farmland would not support a significant amount of biodiversity,” Daily explained. Diversified farms not only provide habitat but also connect otherwise fragmented forested regions.
“I have moved away from the ‘fortress conservation’ model, which focused more on creating protected areas separate from human activities, and see more and more how much potential there is outside of forests,” Hendershot added. The forests are critical; we need them, of course. But I’m always shocked by how essential agricultural management is for biodiversity.”
“We believe the findings of our research are new to science, but in a sense, it merely confirms what Indigenous communities around the world have already known for a long time, which is that humans can and should have reciprocal relationships with the rest of the local ecological community they are part of,” said Tadashi Fukami, a professor of biology in H&S and of Earth system science in the Stanford Doerr School of Sustainability and a co-author of the paper.
In the 1980s and 90s, deforestation was occurring in Costa Rica at the fastest rate ever seen on a country scale. Then, they turned it around — becoming a renowned model of success. By setting up the world’s first countrywide payment for ecosystem services (PES) program, Costa Rica reversed this trend: today, forests cover almost 60% of its land, up from 40% in 1987.
In the coming years, the country hopes to quadruple the area of protected woodland. Any landowner can get money for reforesting even small portions of their land through the existing PES program. The government is also developing a new PES program to encourage farmers to use the best management techniques.
This research will assist Costa Rican officials in better understanding the long-term benefits of various farming systems. “We need to recognize the vital work that many farmers are doing to support biodiversity,” Daily said.