A groomed, grassy field can be good for certain uses, like sports or picnics. But for broader "ecosystem services" — things like plant pollination, disease control, soil quality and climate regulation — the smart money is in meadows.
Meadows are more than just unmowed lawns, though. They are rich, diverse ecosystems, bustling with a wide range of wildlife. And as a new study illustrates, meadows and other natural grassland habitats can be surprisingly beneficial to humans — if we let their biodiversity reach full bloom.
Published in the journal Nature, the new paper was conducted by 60 researchers from nearly three dozen universities. They studied 150 grasslands, examining how species richness and abundance relates to 14 specific ecosystem services. Biodiversity is key, but their research suggests the secret to a great grassland is a bit more complex. And given what's at stake, we'd be wise to pay attention.
For a grassland to reach its full potential, it needs biodiversity at multiple 'trophic levels'. (Photo: Nicholas A. Tonelli/Flickr)
Healthy grasslands host lots of species at various levels of the food chain, also known as "trophic levels." Humans are eroding biodiversity in many of these groups, often by developing grasslands for intensive agriculture. Earlier research has suggested that loss of biodiversity can threaten a grassland's ecosystem services, but those studies didn't examine diversity across multiple trophic groups at the same time.
The new paper is therefore the first to study all groups in a grassland food chain. Its 60 authors collected data on 4,600 species from nine trophic groups — including obscure, easily ignored creatures such as soil microbes and insects.
"Many different groups are important for providing essential ecosystem services. In order for nature to continue 'working' reliably for us, we therefore need to protect biodiversity at all levels in the food chain, including in often overlooked groups such as microbes or insects," says co-author Eric Allan, an ecologist at Germany's University of Bern, in a statement about the study.
Wildlife conservation tends to focus on larger animals like mammals, birds and reptiles, or on high-profile plants like a forest's trees and a grassland's grasses. But while those are certainly worth protecting, they're only part of the puzzle.
"Plants supply biomass which forms the beginning of the food chain, but insects act as pollinators and soil organisms increase soil fertility through the breakdown and retention of chemical elements such as phosphorus," says lead author and University of Bern ecologist Santiago Soliveres. "The more different species there are, particularly within these three groups, the more positive the effect on all services."
An Edith's copper butterfly forages for nectar at Elk Meadow near Stanley, Idaho. (Photo: Katja Schulz/Flickr)
In other words, mere biodiversity isn't enough — a healthy grassland should have biodiversity at multiple trophic levels, since species from each level play interwoven roles. Even if a meadow has lots of plant species, for example, its ecosystem services may suffer if insecticides reduce diversity of pollinators like bees and predators like praying mantises. Likewise, fewer kinds of insects and microbes may thrive if their motley meadow is replaced by a monoculture of mowed grass.
"Our study shows that the functional importance of biodiversity in real-world ecosystems has been greatly underestimated, as a result of focusing on individual trophic groups," the researchers write. "We demonstrate here that the functional effects of multitrophic richness and abundance are as strong as, or even stronger than, those of the environment or land-use intensity."
The 14 ecosystem services they studied fall into four basic categories:
- Supporting services related to nutrient capture and cycling, such as nitrification, phosphorus retention and colonization of roots by symbiotic mycorrhizal fungi.
- Provisioning services related to agricultural value, including the overall quantity and nutrient quality of plants eaten by herbivores.
- Regulating services for nearby crops or climate, such as pest control, resistance to plant diseases, carbon levels in soil, and pollinators like bees and butterflies.
- Cultural services related to human recreation in the ecosystem, such as bird diversity and wildflower cover.
"Collectively, our results show that high species richness in multiple trophic groups is necessary to maintain high levels of ecosystem functioning, particularly for regulating and cultural services," the researchers write.
Mow money, mow problems
Reckless farming can help grasslands become wastelands, as seen in the 1930s Dust Bowl. Yet it's not only possible for farms to coexist with healthy grasslands; it's better, thanks to ecosystem services like those listed above. As with forests — which host bats, owls and other predators that prey on farm pests — leaving grassland around farmland offers an array of natural benefits that can be hard to recreate.
But what about smaller tracts of land, like front lawns and grassy fields? Even if they don't directly replace natural meadows, they often stand where grasslands, forests or wetlands once grew, and how we manage them can still affect biodiversity. Not only does wildlife live in our yards and roadsides, but many migratory animals use them to travel, since parks and nature preserve rarely connect into wildlife corridors.
As MNN's Starre Vartan wrote last year, about 40.5 million acres of lawns exist in the U.S. alone, which is more than double the size of the country's largest national forest. Agriculture and industry may be the main drivers of habitat loss, but anyone who owns a yard or garden can still make a dent in the problem.
Mowing a lawn takes time and money, both for buying a mower and then keeping it fueled. Many lawns also need to be irrigated, which can tax water supplies during droughts. Synthetic fertilizers and herbicides wash into local watersheds, potentially causing even bigger problems downstream. And on top of all that, a patch of clipped, homogenous grass might not support very much biodiversity.
The best alternative depends on location, and meadows aren't right for every climate. Even when they are, simply not mowing may not be enough. A healthy habitat tends to have lots of variety, so rather than just letting a lawn grow unchecked — which may annoy neighbors or violate local ordinances — consider a mix of native ground covers like wildflowers, moss, xeriscaping or a bog garden.
Wherever possible, though, it's worth keeping meadows in mind. Even if there's only room for a tiny one, it could still harbor native plants, insects and soil microbes, promoting the kind of balanced ecosystem that tends to repay the favor.