Estimating the impacts of farmland management on invertebrate welfare: Ruth Feber and Paul Johnson

The caterpillar of a peacock butterfly (Aglais io) sits on a leaf of common nettle. Photo credit: G. Riddoch.

June 16, 2022

In the fields and hedgerows of a working farm five miles from the University of Oxford, millions of insects forage, burrow, mate, fly, and carry out their lives. Activities such as cultivation and harvest can throw them into disarray. For years, University of Oxford Research Fellow Ruth Feber has studied the conservation impacts of agricultural practices on butterflies and moths that inhabit farmland, and now, she plans to leverage her decades of experience to measure welfare in wild insects.

“Butterflies and moths are a fascinating group of insects,” Feber says. “They’re also appealing to people — who doesn’t love the book The Very Hungry Caterpillar? They’re ideal for talking about issues related to invertebrate welfare.”

Though billions of insects live in the world and a growing body of evidence indicates invertebrates may have positive and negative experiences, many questions remain unexplored about insect welfare. Feber’s study — one of seven proposals that Wild Animal Initiative selected in spring 2022 for full funding — aims to address some of those questions. Working with research fellows Paul Johnson and Sandra Baker, Feber will investigate a model for quantifying wild insect health and well-being and use that model to assess the impacts of agricultural practices on caterpillar welfare. 

WHY WE FUNDED THIS PROJECT

Farms take up nearly half of the world’s habitable land, but there is a lack of data about how agricultural management practices might impact wild animals, especially invertebrates. In order to improve welfare for invertebrates, we first need to understand how to measure welfare. This project will explore a model to quantify wild insect health and wellbeing.

What is life like for Lepidoptera?

“There’s increasing evidence showing the complexity of invertebrate experience.” —Ruth Feber

Photo credit: G. Riddoch

Feber’s research gives literal meaning to the term “field work.” She recalls many cold spring nights crawling on her hands and knees along the field margins of the University of Oxford’s farm, searching for tiny caterpillars that live in the crops and plants growing on the farmland. 

Feber says there are billions of wild animals inhabiting agricultural land. Cropland takes up more than 1.2 billion hectares of Earth’s surface and is rapidly expanding. It’s also highly regulated land, where management practices can be modified to improve welfare for the animals living there. Though previous research has studied farmland activities that affect welfare for mammals and birds, it’s much less common to see considerations for insects.

Despite this, Feber says, people instinctively think about invertebrate welfare in their daily lives. 

“A lot of people will save a spider in the bathroom because they don’t like the idea of squashing it or seeing it suffering,” she says. 

Feber sees insect welfare as a growing area of research. She points to related behavioral studies, such as a 2020 study on caterpillars that indicates they behave more aggressively during food shortages. Other studies have explored the effects of pesticides on honey bee social behavior. 

“There’s increasing evidence showing the complexity of invertebrate experience,” she says. 

“If a farmer plows a field when ground-nesting birds are there, everyone understands that has serious implications for wildlife. But rarely do people think about the millions of insects that are affected, and that’s what we’re trying to do.” — Paul Johnson

Photo credit: Ruth Feber

A metric for insect welfare

A marbled white butterfly (Melanargia galathea) rests on field margin. Photo credit: G. Riddoch.

Feber’s previous work has focused mostly on conservation, studying the impacts of land management practices on biodiversity and endangered species. In addition to conservation work, she and Johnson have considered the welfare of individual animals for more than a decade. In 2010, Johnson first pondered the potential of measuring wild animal welfare by adapting a quality-of-life framework commonly used in medicine to compare the value of various medical or surgical treatments. 

“What we want to do is estimate the relative amount of poor welfare associated with any particular agricultural activity,” Johnson explains. 

Feber, Johnson, and Baker will use this framework, called the quality-adjusted life year (QALY), to quantify the impact to invertebrate welfare from various farmland stressors, including reduced access to food, exposure to insecticides, and farm machinery use. They will rely on the Five Domains Model, a tool for assessing animal welfare, to estimate how farmland stressors result in poor welfare for an individual larval insect. Though other researchers have explored extending the concept of QALYs to animal welfare, this will be the first to extend it to wild invertebrates.

For example, cutting hedgerows at a certain time of year might take food away from caterpillars who rely on that vegetation. Since nutrition is one of the Five Domains, the researchers could conclude that starvation leads to poor welfare outcomes and premature death for the caterpillars. The QALY framework will provide a methodology  for  comparing the welfare cost of different farming activities. 

It’s challenging to measure the experiences of any wild animal, let alone a wild insect. As a result, this study will focus on indicators of stress, such as behavior and morphology. For example, lack of food might affect both these indicators, as might exposure to changes in temperature. Similarly, pesticides can have a broad range of sub-lethal effects on insect larvae. 

Because this is a desk-based study, the researchers plan to complete a literature review and plug pre-existing data into a model, avoiding the need to gather new field data. Very little research exists in this area, so the study represents an important first step in finding ways to evaluate insect welfare.

“If a farmer plows a field when ground-nesting birds are there, everyone understands that has serious implications for wildlife,” Johnson says. “But rarely do people think about the millions of insects that are affected, and that’s what we’re trying to do.”

Considering caterpillars

In the UK and across the world, agricultural land hosts millions of wild insects. Photo credit: Ruth Feber.

In Europe, agri-environment schemes incentivize farmers to manage their land in ways that protect or increase biodiversity. With more research and better models that estimate how farming practices impact wild insect welfare, Feber says, conservationists and policy makers could include welfare when making decisions about farmland management. Insect welfare considerations aren’t currently factored into land management policies, but studies like this one can provide initial models where few or none exist. 

For example, cutting wildflower field margins might not affect adult butterflies who are able to fly and find nectar elsewhere, but the much less mobile caterpillars could starve from the loss of vegetation in their limited range. Decision makers could consider welfare costs alongside other costs or benefits of specific farming activities.

“There may be a poor welfare outcome for some insects even if you’re doing positive conservation management,” Feber says. 

Johnson and Feber agree that the relatively unexplored area of wild insect welfare makes it particularly appealing to study, and they hope their study will lead to greater interest from academia and beyond.

“Many questions about invertebrate welfare are completely open,” Johnson says. “It’s a simple thing that makes it so academically interesting.”

“The multidisciplinary nature of it is exciting, as well,” Feber adds. “It involves conservation, land management, and social science — lots of different interests can be involved in this work.” 

Feber’s proposed study is funded by Wild Animal Initiative’s Grants Program. If you are a researcher or student interested in pursuing wild animal welfare science, please take a look at our latest call for proposals. Wild Animal Initiative is accepting expressions of interest through June 30, 2022. 

RELATED RESEARCH

Ruth Feber and Sandra Baker, with their colleagues Eva Raebel, Neil D’Cruze, and David Macdonald, published a paper in the journal BioScience that analyzed media mentions of wild animal welfare in the UK. The paper, titled "Some Animals Are More Equal than Others: Wild Animal Welfare in the Media," was published in 2017.

This is the second story in a series of features on our spring 2022 cohort of grantees. Please subscribe to our newsletter to get future stories delivered straight to your inbox.