Image Credit: Mainaksinghabarma, CC BY-SA 4.0, Image Cropped

Increasing cover of natural areas at smaller scales can improve the provision of biodiversity and ecosystem services in agroecological mosaic landscapes (2022) Rosenfield et al., Journal of Environmental Management, https://doi.org/10.1016/j.jenvman.2021.114248

The Crux

While nature documentaries insist on portraying the natural world as entirely separate from human life, the fact is that ‘natural’ areas exist side by side with, and often within a mosaic of, human and semi-human (think agricultural or grazed) ecosystems. These natural ecosystems provide a wide array of services – they hold biodiversity, suck carbon in from the atmosphere, maintain clean water, and even regulate local temperatures.

With a growing global population, maintaining these ecosystems unfortunately isn’t as simple as leaving the natural world alone. Development needs to be planned with these ecosystems in mind, and choosing exactly where to leave them intact is tricky. Scale is a big problem here – does leaving one big patch of forest untouched give the same benefits as leaving many smaller patches dotted throughout a landscape? That’s what today’s researchers were trying to answer.

What They Did

Today’s researchers studied a large region in south-west Ontario, Canada. The region contained a number of different ecosystems, which they broke into natural, agricultural, and urban areas. They selected regions across the different areas to test for different indicators of ecosystem services:

• Biodiversity – in this case the abundance and species richness of different plant species
• Carbon storage – in this case measured by the mass of trees above ground throughout the regions
• Local climate regulation – the ability of an ecosystem to regulate local temperatures
• Water quality – checking the concentration of different minerals in local water sources

They then compared these to the percentage of these regions which were covered by natural, agricultural, or urban areas.

Did You Know: Cultural Landscapes

Large agricultural clearance often creates fragmented landscapes and damages population which depends on large, connected landscapes. Yet at a small scale, very localised grazing often create small patches that break up the usual landscape and can sometimes increase species richness on a larger scale. It’s a phenomenon that has often led the idea of ‘cultural landscapes’ being deemed necessary for a healthy landscape. Yet often these landscapes are a fairly recent phenomenon, and not really representative of the ‘natural state’ of an ecosystem. Furthermore, they may increase species richness on a small scale, but if they expand too much those effects start to be outweighed by their fragmenting effects.

What They Found

The most notable patterns came with an increase in natural land cover. Where there were higher proportion of natural land, biodiversity increased and local temperature decreased at all spatial scales. Aboveground carbon and water quality also increased with increasing natural land, though only at smaller scales.

Increasing urban land area led to lower biodiversity and higher temperatures across all scales, while the only pronounced effect an increase in agricultural land had was to decrease local temperatures.

Problems

Obviously a high level of plant species richness does not necessarily translate to high species richness of other organisms like fungi and animals. Species richness itself can be misleading, as high abundances of one particular species and small abundances of others will give the same value as a more even spread across the region. However, a more intensive survey would have increased the workload tenfold, and I understand why the authors went for plant diversity, which generally can be a good indicator for more comprehensive estimates.

So What

While there are many who argue for the positive influence of agricultural areas on the environment, this study suggests that natural ecosystems are by far the most important contributors to important ecosystem services. The fact that this was even more pronounced on smaller spatial scales means that a mosaic-like spread of natural areas throughout a landscape is beneficial, rather than isolated patches of forest dotted throughout larger areas.

These are important notes for environmental planners, who need to be considering exactly where agricultural areas (and further urban encroachment) should lie in the future. Ecosystems provide us with a host of tangible benefits, and we need to preserve these, not to mention the bevy of species that exist within them.

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Dr. Sam Perrin is a freshwater ecologist who completed his PhD at the Norwegian University of Science and Technology and will quite happily go for long walks in the forest in order to skip work and say he “got lost”. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.