Europe's butterflies are vanishing as small farms disappear

Castelló d’Empúries, SpainEach week for the last 25 summers, biologist Constantí Stefanescu has walked a line through a series of fields in Catalonia, counting butterflies. On a sun-beaten day last July, near where the Pyrenees Mountains slip into the Mediterranean Sea, he stepped into what had once been the most butterfly-rich meadow of them all. In the early years, he could easily count 50 or 60 silver-studded blue butterflies here, along with many other pollinators, all drawn by a carpet of lupine, clover, and other wildflowers.

The meadow was so hospitable because it had been maintained by a farmer who did things the old-fashioned way—mowing the field just once or twice a year and using the hay to feed his animals through the winter. But a few years after Stefanescu started monitoring butterflies here, the farmer abandoned the field. Soon, brambles choked out the wildflowers, then came brush, and eventually a forest emerged. A few butterfly species adapted to woods arrived. But the rich diversity Stefanescu had once tallied was gone.

“If I look at the records from 25 years ago, it’s a shock,” says Stefanescu, who runs the Catalan Butterfly Monitoring Scheme, which tracks the region’s butterfly populations at more than 140 sites, with the help of dozens of citizen scientists.

Some 90 percent of Catalonia’s butterfly species live in open space and thrive in flower-rich grasslands, as they do in most temperate climates. But across Europe these butterflies are undergoing huge declines. According to one of the European Union’s most comprehensive indices, grassland butterfly abundance dropped by 39 percent between 1990 and 2017. Catalonia is an extreme example of this continent-wide wave of biodiversity loss: Over the last 25 years, populations of the most common grassland species have declined here by 71 percent.

Butterflies, like other pollinators, are being squeezed from two sides. In some places, as small-scale livestock farms give way to industrial agriculture, butterfly-friendly meadows are being aggregated into much larger fields of a single crop like corn or sunflowers. In others, pastures and fields are being abandoned and are slowly turning to forest. Both trends threaten butterflies.

Standing in the forest shade, with a net in one hand and a clipboard in the other, Stefanescu says there’s little chance this spot will ever return to the prime grassland butterfly habitat it was a generation ago. Instead, he expects it will further deteriorate. “This is the start of local extinction,” he says. 

A continent-wide decline

Butterfly monitoring schemes, like the one Stefanescu coordinates, are in place across Europe, some stretching back decades. Because they all use similar methodology, researchers and citizen scientists have generated a robust dataset that provides crucial information about how butterflies are faring. This information increasingly serves as a rough proxy for the health of other pollinators such as bees and for the environment in general. What the data are signaling is troubling. 

One in five European butterflies are considered threatened or nearly so. The Netherlands has lost half of its butterflies since 1990. And insect populations in general are collapsing, according to a growing body of research, most famously the Krefeld study from 2017, which found the abundance of insects in German nature reserves fell by 75 percent over a 27-year period.

Farmland birds, which share many of the same habitats as butterflies and feed on caterpillars, have also declined drastically. France, for example, has lost a third of these species in the last 30 years.

The habitat supporting many of these insect and bird species is in trouble, too. More than three-quarters of the grasslands in the European Union (EU) are in “unfavorable” conservation status—a broad designation that can mean anything from needing improvement to being lost entirely. In the U.K. and the Netherlands, for example, less than 5 percent of semi-natural grasslands remain.

Agriculture is considered the main driver of species loss worldwide, according to the UN Environment Programme. But when it comes to protecting grasslands and the butterflies, birds and other insects that live there, agriculture can be either a positive or negative force, depending on how it’s practiced.

Intensive farming is clearly bad for biodiversity. Few wild plants and animals can survive practices like planting vast fields with a single crop, pesticide use, and frequent mowing and plowing. Nitrogen pollution, which comes from both fertilizers and concentrated livestock farms, boosts the growth of grasses that crowd out plants that butterflies need.

But counterintuitively, too little human intervention harms these grassland ecosystems, too—as Stefanescu’s data shows—and thus butterfly populations. “Forest encroachment is one of the reasons behind this collapse,” he says, “but intensification is the other side.”

After Stefanescu finishes his butterfly count, he drives for a few minutes along a road that winds through corn and sunflower fields—land that was once hay meadows. He pulls off next to a cornfield, where the rustling stalks come right up to the roadside. “The edges are completely gone,” he says.

Part of the reason why less intensive, traditional agricultural landscapes are so biodiverse is because they’re a mosaic: Fields, woodlots and orchards are bordered by rock walls, hedges, and uncultivated margins. The different human uses leave space for wild plants and animals, which find refuge in these interstitial zones. The result is a sort of domesticated wilderness.  

But mechanization and farm subsidies have encouraged farmers to merge smaller plots into large, uniform fields and to pack more animals into tighter spaces. And while the EU has set specific goals for protecting biodiversity, it concedes that these programs have largely failed. To address farming’s role in the biodiversity crisis, it has recently adopted measures such as the Farm to Fork Strategy and the Biodiversity Strategy. What really governs how food is produced in Europe, though, is the farm subsidy program, called the Common Agricultural Policy, which cost $70.4 billion in 2019 and accounts for more than a third of the EU budget.

Instead of incentivizing farmers to make room for wildlife, that program still largely encourages the expansion of monocultures, like the giant cornfield Stefanescu has stopped to show me.

“This is a single habitat,” he says, gesturing at the sea of green stalks. “And it’s a hostile one.”

Grasslands also store carbon

Aside from being biodiversity hotspots, grasslands and savannahs store tremendous amounts of carbon—some 660 billion metric tons of it globally. In North America grasslands can sequester as much carbon in their soil as tropical forests store as biomass. And yet, they are one of the least protected ecosystems on the planet, largely maintained by farmers and ranchers. Just how ancient grassland habitats are is often underappreciated, but many predate modern humans. They were shaped by glaciers, long-extinct giant herbivores, and fire.

Some common prairie grasses can live for hundreds or even thousands of years. But, unlike ancient forests, old-growth grasslands’ richness and carbon-storing potential is hidden underground in vast root systems, says Joseph Veldman, an assistant professor of ecology and conservation biology at Texas A&M University. 

Lately a new threat to grasslands has emerged: tree-planting campaigns. Two years ago Veldman was one of many critics of a widely-covered paper that called tree planting the most effective way to mitigate climate change and claimed a trillion trees could be planted on Earth. The research was “inaccurate and misleading,” according to Veldman, and the tree-planting effort it implied would have “gravely threatened” grasslands and savannahs. 

The study authors have since corrected the study and backed off its larger claims. But the idea that planting trees will save us persists, Veldman says, and is particularly appealing to industry leaders and policymakers who don’t want to reduce our reliance on fossil fuels.

Meanwhile, in places like Spain, and the overgrown meadow where Stefanescu counts butterflies, abandoned farmland is turning into forest by default. After decades of rural depopulation, a quarter of the country is now covered in forest—three times more than in 1900.  Forest cover, which includes plantations, is increasing by about 1 percent per year on average, mostly through natural regeneration.

To some conservationists, this looks like a win: It's a chance to cede marginal, essentially unwanted land to nature. Already, woodland bird species and large mammals like wolves and ibex are making a comeback in Spain.

But just letting unused farmland go wild isn’t the answer, says Deli Saavedra, head of landscapes at Rewilding Europe. Rewilding—a movement to restore habitats, often by introducing apex predators and large herbivores like feral horses to degraded landscapes—has gained traction across Europe in recent years. Grazing animals keep landscapes “functional,” Saavedra says, by maintaining open grassland and reducing fire risk.

Saavedra’s group is in the early stages of a project that would reintroduce semi-wild grazing animals to more than two million acres of abandoned pasture in the Iberian Highlands in central-eastern Spain. “There’s a missing piece, and that’s herbivores,” he says.

Pop-up protection

High in the Pyrenees, near the border of France and Spain, another, much scrappier, effort is underway to try to save one of Catalonia’s most iconic butterflies—the mountain Alcon blue, which has large, blue-and-beige wings. Biologists Irene Figueroa and Guillem Mas chug up a steep dirt track in a four-wheel drive truck they call Tete—a Catalan term of endearment for brother. Arriving in a remote pasture where wildflowers grow hip-high, Figueroa spots the Alcon blue’s host plant, the cross gentian.

Pushing aside its sturdy blue flowers, she finds the butterfly’s eggs—tiny white dots the size of pinheads—laid close to a bud. Alcon blues are threatened in Europe and have declined over much of their range. Part of the problem for this one, the mountain Alcon blue, is that it only thrives in a very narrow habitat, which has been drastically reduced, and depends on a single host plant to reproduce. Alcon blue butterflies also have a parasitic relationship with certain species of ants. Using pheromones and sound, the butterflies trick the ants into sheltering their caterpillars in their colonies over the winter. “There are very few sites that meet all the criteria,” Figueroa says.

Figueroa and Mas specialize in what might be called pop-up nature protection. Instead of going through official governmental channels to protect species, which can take years, they prospect for threatened plants, animals, or even habitats like flowering meadows. As part of their conservation and restoration nonprofit, Paisatges Vius, or Living Landscapes, they create micro-reserves to quickly protect at-risk species in the fragments of land where they are hanging on.

But that doesn’t mean fencing humans out—instead, they negotiate directly with landowners on how to manage the landscape. In the best of cases, it’s just a simple accord to keep doing whatever they’ve been doing, and a promise to contact Figueroa and Mas if they plan on making a change. In other cases, they ask landowners to alter their practices, and compensate them for any losses that might entail.

In this meadow, for example, they’ve asked a rancher to delay and reduce mowing. That will let the Alcon blue live out its whole life cycle, and also allow Figueroa and Mas to collect wildflower seeds that they’ll use to restore degraded grasslands nearby, which will hopefully expand the butterfly’s habitat. To compensate the farmer for mowing less, they’re buying him hay from other farms. And to cement goodwill with local farmers, they've recently repaired some of the roads that wind through the pastures.

This is not quick or easy work, Mas says. Environmentalists and farmers often have an adversarial relationship, and even some of the farmers they collaborate with think it’s more bother than it’s worth. Conservation is increasingly complex, Mas says. “It was once just habitat loss, but now it’s so many things: Invasive plants, climate change, chemicals…even if you do everything right, there can be a factor like climate change that just changes everything.”

The ant that the Alcon blue relies on is sensitive to changes in soil temperature, for example.

“This is something we won’t really be able to control in the future,” Mas says, trailing off.

At that moment, standing on the slope as butterflies and bees feed on the blue-and-purple flowers, the work seems so daunting: collecting seed, replanting prairies, nurturing alliances with reluctant ranchers with bales of hay and truck-window to truck-window chats on rutted mountain roads. But maybe that’s just what finding balance between humans and nature looks like on the ground.

“In these old landscapes that have been used by humans for centuries or even millennia, the highest level of diversity is reached when there is collaboration,” Stefanescu says.