- Researchers studying how species respond to repeated and rapid land cover changes say more focus needs to be placed on preserving the biodiversity value of human-dominated landscapes.
- With much of the world’s intact ecosystems now modified by humans, the study warns that without careful management, species will be lost each time land is converted from one land-use type to another, such as when forestry is transitioned to plantation or agriculture.
- The researchers call for biodiversity impact assessments when land is proposed for conversion, regardless of whether it is intact primary habitat or considered “degraded” land.
- They also recommend the identification, preservation and restoration of natural features of landscapes, such as forest fragments, large and old trees, and wetlands, which can serve as vital refuges for species between successive land conversions.
Humans have transformed the planet to a staggering extent. Studies estimate that, as a species, we’ve modified at least three-quarters of the Earth’s land surface. Over time, vibrant mosaics of forest, grassland and wetland have been replaced with our road networks, bustling cities, and industrial-scale pastures, plantations and croplands.
With so much of the globe under our influence, more focus needs to be placed on recognizing and preserving the biodiversity value of human-dominated landscapes, says an international team of researchers in a new review study published in Global Ecology and Conservation.
“The idea that we can have nature conservation of biodiversity in some parts of a landscape, country, or continent, and then have our food production landscapes and human-dominated landscapes in separate areas, I think is a bit ridiculous,” study co-author Ben Scheele, an ecologist at Australian National University, told Mongabay. “We really have to be serious about having wildlife in areas that are heavily human-modified.”
To this end, Scheele and his colleagues from Australia and the United States present a new conceptual framework, based on ecological theory, which they say will help resource managers and conservation biologists anticipate how species living in modified landscapes are likely to respond to repeated and rapid changes in land use.
While individual species responses will vary according to local conditions, the authors broadly conclude that without careful management, species will be lost each time land is converted from one land cover type to another, such as when forestry is transitioned to plantation or agriculture.
Repeated conversion of already modified land is increasingly prevalent in many parts of the world, according to the study, and is set to intensify in the future due to the combined effects of climate change, advances in technology, shifting markets and the pressures of an ever-expanding human population.
In Brazil, tracts of the Atlantic Forest that were initially cleared for coffee plantations have subsequently been converted for livestock grazing. In Australia, swaths of forest cleared to make way for livestock farms have since been planted with almond trees to take advantage of the lucrative nut market. Meanwhile in Southeast Asia, vast seas of oil palms dominate many landscapes that were once tropical forest and that underwent initial conversion to rubber plantations.
Averting species losses during such transitions should be treated as a matter of urgency by land managers and conservationists alike, Scheele said, adding that a major concern is “shifting baselines,” whereby people get used to the presence of fewer and fewer species with each successive land conversion.
A key solution lies in protecting natural features of landscapes, what the authors term “biological legacies,” that can serve as vital refuges for a range of species between successive land conversions. Studies in oil palm plantations, for instance, show that “islands” of natural forest boost biodiversity and improve ecosystem functioning while also maintaining crop yields.
Retaining and, where possible, restoring these natural features of previous landscapes make it more likely that species will be able to adapt to changes in their environment, Scheele said.
With this in mind, the authors call for thorough environmental and biodiversity assessments when land is proposed for conversion, regardless of whether it’s intact habitat or degraded land. These assessments could identify features worth preserving and also track changes in species diversity over time. The researchers propose the integration of such surveys with existing land conversion planning processes and government policy.
Scheele acknowledged, however, that implementing environmental safeguards can be fraught with challenges in many parts of the world, even when there is risk of losing primary intact habitat. “It’s even harder to get traction for mechanisms to be put in place for landscapes that have already been heavily impacted by humans,” he said, “so we really need to think about being realistic.”
Roman Carrasco, an associate professor of environmental sustainability at the National University of Singapore, who was not involved in the study, said it presents a new way of approaching land-use conversion that a lot of prior research has overlooked.
“The framework they propose is great because in most cases, we tend to think of land use changes as one-offs,” Carrasco told Mongabay. “We think of, say, forests becoming oil palm. But especially in Southeast Asia, land use change is very dynamic and ecological changes are going to be different depending on [multiple factors].”
Carrasco, who has studied broad patterns of land conversion across Southeast Asia, including the conversion of rubber plantations to oil palm, said land managers and companies can do more to safeguard biodiversity. “We shouldn’t just assume that land that’s been converted is ‘degraded’ and so we can give up on it. There are still many high-quality modified landscapes that could contain a lot of biodiversity.”
Many oil palm companies take a simplistic approach to avoiding deforestation, Carrasco said, by simply planting palm crops on already modified land. But since some of that land could in fact support many species, a more nuanced approach is necessary. Extra safeguards, including assessment of natural features and other important “legacies” of previous landscapes, should be implicit in the planning process, he said.
“Planting in ‘degraded’ land doesn’t automatically mean that you’re not creating some ecological damage,” Carrasco said. “It’s important to give more consideration to the history of land use when making new concessions. Set-aside areas of original natural habitat are also very important [and] don’t need to be at odds with economic returns. They can be very beneficial even for the plantation companies themselves [by providing] natural pest control, pollination services and flood prevention.”
Banner image: An oil palm landscape in Malaysian Borneo. Image by Rhett A. Butler for Mongabay.
Carolyn Cowan is a staff writer for Mongabay. Follow her on Twitter @CarolynCowan11.
Citations:
Lindenmayer, D., Scheele, B. C., Lavery, T., & Likens, G. E. (2023). Biodiversity response to rapid successive land cover conversions in human-dominated landscapes. Global Ecology and Conservation, 45, e02510. doi:10.1016/j.gecco.2023.e02510
Ellis, E. C., Gauthier, N., Klein Goldewijk, K., Bliege Bird, R., Boivin, N., Díaz, S., … Watson, J. E. (2021). People have shaped most of terrestrial nature for at least 12,000 years. Proceedings of the National Academy of Sciences, 118(17). doi:10.1073/pnas.202348311
Zemp, D. C., Guerrero-Ramirez, N., Brambach, F., Darras, K., Grass, I., Potapov, A., … Kreft, H. (2023). Tree islands enhance biodiversity and functioning in oil palm landscapes. Nature, 618(7964), 316-321. doi:10.1038/s41586-023-06086-5
Jayathilake, H. M., Jamaludin, J., De Alban, J. D., Webb, E. L., & Carrasco, L. R. (2023). The conversion of rubber to oil palm and other landcover types in Southeast Asia. Applied Geography, 150, 102838. doi:10.1016/j.apgeog.2022.102838
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