A Global Butterfly Index Could Advance Insect Conservation Worldwide
Lead image by Karen Hogan / iStock
By Federico Riva
About 70 per cent of the species on Earth are insects. They are fundamental components of most ecosystems: they comprise half of the biomass on the planet, pollinate flowers, decompose dead organic matter and play multiple roles in food webs. They are quite literally everywhere, including in and around our homes, but they have also been declining at alarming rates in many places.
The societal implications of this potential “insectageddon” could be catastrophic, including losses in human food production. However, confirming suspicions of global declines is difficult because we lack reliable data on insect populations in many parts of the world.
We simply don’t have the infrastructure around the planet that would allow us to track insect populations altogether. That means we don’t know how insect populations are responding to different global changes, and we might be failing to design effective conservation policies and track whether current actions are working.
Efforts to rapidly generate global indicators of insect population trends are therefore crucial. In our recently published paper, colleagues and I explain how a global butterfly index could help track butterfly populations worldwide — and how we can reach this important objective.
Butterflies: The poster child of insects
One reason why insects have been neglected in conservation is that they are often ignored — if not feared — by many people. Many of us have been brought up to be cautious around insects, whether they’re bees, spiders or other critters.
There is, on the other hand, broad interest in vertebrate species. Bird-watching has been part of human societies for hundreds of years. The fact that larger animals capture public interest has arguably stimulated global efforts to calculate indicators of trends in their populations, like the Living Planet Index by the World Wildlife Fund and other organizations.
While insects have generally not benefited from the attention that other animals have received, butterflies are one exception to this rule. These insects, with their captivating patterns and colours, have long fascinated people and have been represented in many traditions across cultures.
Our love for butterflies is reflected in a substantial history of monitoring. In the 1970s, the British entomologist Ernest Pollard initiated the practice of recording butterfly populations on his butterfly walks in England. Fifty years later, hundreds of “Pollard walks” are done across Europe and in many other regions of the world.
Recording the presence of a species in an area is important work. However, equally fundamental are efforts that capture changes in insect populations over time. Nonetheless, a global synthesis of butterfly population monitoring programs has, to date, been missing.
A global butterfly index
Our recent paper fills that gap. We co-ordinated an international consortium with the goal of better understanding opportunities and challenges for calculating a global butterfly index that captures trends across butterfly populations worldwide.
Bringing together scientists from all continents except Antarctica, we were able to collate an incredible dataset including more than 45,000 population trends for over 1,000 butterfly species. We used this data set to:
- Identify where current efforts stand in terms of taxonomic and spatial coverage of the global butterfly fauna.
- Calculate the first version of a global butterfly index.
- Evaluate gaps and limitations to address before moving forward.
Despite an unprecedented effort, we found that only populations of around five per cent of species worldwide have been monitored.
It’s important to note that the data set is mostly concentrated in Europe and North America and biased in favour of generalist species (those able to survive in diverse environments) as well as species easier to detect.
Nonetheless, we found that species are on average declining, and sensitive butterflies expected to suffer from global change tended to decline more steeply than the rest of our sample. Populations outside of Europe and North America were too sparse to support robust inferences.
Global Butterfly Week
Developing this study left us with a few lessons learned. There is substantial work to do if we aim to calculate a truly global indicator of butterfly population trends.
For instance, many parts of the Global South will need support to swiftly develop national monitoring programs, and research in the tropics is needed to better understand what monitoring methods would work best in hyper-diverse regions.
The good news is that butterflies are already one of the most visible and monitored insect groups, which will ameliorate the challenges associated with developing indicators of insect populations. Existing monitoring schemes can provide a template upon which new initiatives can be developed.
Ultimately, developing a global butterfly index will be key to providing long-overdue tracking of insect population changes. Crucially, it could also act as a flagship for broader insect conservation.
Governments are expected to set measurable biodiversity targets in line with their commitments under international agreements such as the Kunming-Montreal Global Biodiversity Framework. However, insects remain largely overlooked in these targets, and it’s impossible to set meaningful targets without robust indicators.
Developing a robust butterfly index is therefore fundamental to help guide conservation and to better understand the scale of the biodiversity crisis, as well as to communicate it to the public.
Butterflies carry a strong emotional value. That can help build support for conservation in a way that less appreciated insects cannot achieve.
Our consortium is helping to create such momentum: this year, members of our team are kick-starting a Global Butterfly Week and conversations around formalizing an international organization are under way.
We are hoping that colleagues interested will join us for the next iterations of these projects. Please reach out.
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Federico Riva is an assistant professor in biology at Carleton University.
This article is republished from The Conversation under a Creative Commons licence. All photos provided by The Conversation from various from various sources.
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