Source: The Conversation – in French– By Federico Riva, Assistant Professor, Department of Biology, Carleton University
About 70% of the species present on Earth are insects. They are essential components of most ecosystems. Representing half of the planet’s biomass, they pollinate flowers, decompose dead organic matter, and play multiple roles in food webs. They are literallyeverywhere, including in and around our homes, but their populationdecreases at an alarming rate in many places.
The societal implications of this potential “insectageddoncould be catastrophic.Losses in human food productioncould notably occur. However, it is difficult to confirm suspicions of global decline, as we lack reliable data on insect populations in many regions of the world.
We simply do not have, on a global scale, the infrastructure that would allow us to monitor all insect populations. This means that we do not know how insect populations respond to various global changes, and that we might fail to design effective conservation policies or to verify whether current measures are effective.
It is therefore crucial to strive to quickly generate global indicators on trends in insect populations.In our recently published article, my colleagues and I explain how a global butterfly index could help track butterfly populations worldwide – and how we can achieve this important goal.
Butterflies: the typical example of insects
(Federico Riva)
One of the reasons why insects have been neglected in the field of conservation is that they are often ignored –even feared– by many people. Many of us have been raised to be cautious around insects, whether bees, spiders, or other little creatures.
There is, however, a broad interest in vertebrate species. Bird watching has been part of human societies for hundreds of years. The fact that larger animals attract public interest has undoubtedly stimulated global efforts to calculate indicators of trends in their populations, such as theLiving Planet Indexfrom the World Wide Fund for Nature (WWF) and other organizations.
Although insects have generally not received the same attention as other animals, butterflies are an exception to this rule. These insects, with their captivating patterns and colors, have long fascinated people and are represented in many traditions across cultures.
Our love for butterflies is reflected in a long history of monitoring. In the 1970s, British entomologist Ernest Pollard initiated the practice of counting butterfly populations duringhis walks in England. Fifty years later, hundreds of “Pollard walks” are organized across Europe and in many other regions of the world.
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Recording the presence of a species in an area is an important task. However, efforts to track changes in insect populations over time are equally fundamental. Nevertheless, a global synthesis of butterfly population monitoring programs had been lacking until now.
A global butterfly index
Our recent article fills this gap. We coordinated an international consortium with the aim of better understanding the opportunities and challenges related to calculating a global butterfly index that reflects trends in butterfly populations worldwide.
By bringing together scientists from all continents except Antarctica, we were able to compile an incredible dataset comprising more than 45,000 demographic trends for over 1,000 butterfly species. We used this dataset to:
(Unsplash/David Clode)
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Determine the current status of efforts in terms of taxonomic and spatial coverage of the global butterfly fauna.
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Calculate the first version of a global butterfly index.
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Assess the gaps and limitations to be addressed before moving forward.
Despite an unprecedented effort, we found that only populations of about 5% of global species have been monitored.
It is important to note that the dataset is mainly concentrated in Europe and North America and that it is biased in favor of generalist species (those capable of surviving in diverse environments) as well as species that are easier to detect.
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Nevertheless, we have observed that species, on average, are in decline, and that thebutterflies sensitive and likely to suffer from climate changetended to decline more sharply than the rest of our sample. Populations outside Europe and North America were too sparse to allow for solid conclusions.
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World Butterfly Week
The completion of this study has allowed us to draw some lessons. There remains a considerable amount of work to be done if we want to calculate a truly global indicator of butterfly population trends.
For example, many regions in the South will need help to quickly set up national surveillance programs, and research in tropical regions is necessary to better understand which surveillance methods would work best in these hyperdiverse regions.
The good news is that butterflies already constitute one of the most visible and monitored insect groups, which will mitigate the difficulties related to developing indicators on insect populations. Existing monitoring programs can serve as a model for developing new initiatives.
Ultimately, the development of a global butterfly index will be essential to provide long-awaited monitoring of changes in insect populations. Most importantly, it could also serve as a spearhead for broader insect conservation.
Governments are supposed to set measurable objectives in terms of biodiversity, in accordance with their commitments made within international agreements such as theKunming-Montreal Global Framework for Biodiversity. However, theinsects remain largely neglectedin these objectives, and it is impossible to set meaningful goals without reliable indicators.
The development of a reliable index on butterflies is therefore fundamental to guide conservation efforts, better understand the extent of the biodiversity crisis, and raise public awareness. Butterflies have strong emotional value. This can help generate support for conservation in a way that less appreciated insects cannot achieve.
Our consortium contributes to creating such a dynamic: this year, members of our team are launching aWorld Butterfly Weekand discussions are underway regarding the creation of an international organization.
We hope that interested colleagues will join us for the next editions of these projects. Please do not hesitate to contact us.
Federico Riva benefited from funding under the Horizon program.
–ref. A global butterfly index could advance insect conservation –https://theconversation.com/a-global-butterfly-index-could-advance-insect-conservation-280304