Championing the underbug

Monika Böhm

The latest findings from the Living Planet Report 2016 paint a bleak picture for the future of wildlife based on studies of vertebrate populations.

Yet creepy crawlies, bugs or as they are accurately called, invertebrates, who are often overlooked when it comes to the conservation and monitoring of species, make up the majority of the world’s biodiversity. 

Monika Bohm, Louise McRae and Valentina Marconi are among the ZSL conservationists behind the stats within the report and explain why raising the profile of invertebrates is an important challenge they are working hard to address.

One of the Phobaeticus genus in the Bugs! exhibit at ZSL London Zoo.

The Living Planet Report 2016

The findings of WWF’s Living Planet Report 2016, that wildlife populations have declined on average by 58% since 1970, have been remarkably well covered by the global media over recent weeks.

Behind the headlines is the Living Planet Index (LPI), one of the two global biodiversity indicators we are working on here at the Institute of Zoology at ZSL. It uses time series data for vertebrate populations, gathering information from around the world to track changes over time. 

"Hang on! Did you say a biodiversity indicator based on vertebrate population trends? But isn't most of our biodiversity invertebrates?". Well, yes, of course it is. But unfortunately there is a lack of population trend data for invertebrates.

While popular monitoring schemes such as counting birds and camera trapping mammals, and the subsequent indicators built from them, are useful to gauge how biodiversity is doing, they are not as representative as they ideally should be.

Nevertheless, this year's Living Planet Report for the first time featured data on population trends in butterflies which showed a 33% decline between 1990 and 2012.

Mind you, European grassland butterflies only, but it's a starting point. And this is finally getting us to the point we are trying to make.

Vertebrate and invertebrate known species numbers
Components of biodiversity: Proportion of known species that are vertebrates, invertebrates or plants and fungi.

New approaches

Here at the Institute's Indicators and Assessments Unit, we are working hard to get invertebrates onto the global conservation map. This is where our second biodiversity indicator, the Sampled Red List Index (SRLI), comes in.

The SRLI is a collaboration with the International Union for Conservation of Nature (IUCN).

The idea behind the SRLI is to broaden our knowledge of the status of species by running extensive assessments of extinction risk for previously underrepresented species groups, particularly inverts and plants .The latter has been carried out by our friends at Royal Botanic Gardens Kew.

Such assessments are carried out under a framework provided by the  IUCN Red List of Threatened Species. Which, curiously, is neither just a list of species, nor features only threatened species.

It provides a scale of extinction risk, from low to high, covering all species from common, widespread ones to those in dangerous decline or small population sizes or restricted ranges. That's the IUCN Red List in the tiniest of nutshells (or, in fact, snail shells).

For the SRLI, we have selected a number of species groups from invertebrates and plants as well as some vertebrates, such as fish and reptiles that are also still underrepresented on the Red List, and we have either: 

  • Carried out comprehensive assessments for all species where their groups comprise of less than 1,500 species or
  • Carried out sampled assessments of 1,500 species randomly selected from the species list for that group where groups are megadiverse. And some of these groups can be rather large, for example there are around 20,000 species of butterflies in the world.

The idea is that these sampled assessments give a broad depiction of what is happening within the species group in question and accurately show trends over time.

Dragonfly
Invertebrates are all around us – but are often overlooked in conservation prioritisation and biodiversity indicators. That is soon set to change.

The results

Assessments such as these have been carried out for freshwater crabs, dragonflies, reef-building corals, crayfish and lobsters, freshwater molluscs, and yes, fish and reptiles too.

In fact, reptiles were one of the first groups completed and now provide an important data source to test different approaches for carrying out these extinction risk assessments which invertebrate groups are also likely to benefit from.

Assessments are still ongoing for cephalopods (that's octopus, squid, cuttlefish and nautilus), dung beetles, and butterflies.

Overall, our unit has been or is still involved in nearly 10,000 invertebrate assessments for the IUCN Red List.

In many instances, this has felt like a Herculean task. But we have things to show for it, namely a vastly improved knowledge on the extinction risk and conservation status of invertebrates.

The results show that overall invertebrate extinction risk is similar to extinction risk in vertebrates with around 1 in 5 species threatened with extinction. And that freshwater species and corals are particularly hard-hit: 32% of freshwater crabs and crayfish, 29% of freshwater molluscs and 33% of reef-building corals are threatened with extinction.

Threatened status across species groups
Threatened status across species groups, as shown in our 2012 report “Spineless: status and trends of the world’s invertebrates” . EX – Extinct, CR – Critically Endangered, EN – Endangered, VU – Vulnerable, NT – Near Threatened, LC – Least Concern, DD – D

Next steps

So what next? Two things:

Firstly our SRLI species groups currently only have a status point, i.e. we know what their extinction risk was in the year of the assessment.

We do not yet know the trend of extinction risk over time in these groups.

We could wait for ten years until current assessments are out-of-date and a reassessment is required for the IUCN Red List. Hardly a proactive approach!

Instead, we are trialling how to best retrospectively assess species for time points in the past, using expert knowledge, literature, latest knowledge on habitat declines and so on, or using future scenarios to project extinction risk into the future, based on what we know about threats and species.

Last week, we managed to present the first trend over time in reptile extinction risk, using retrospective assessments.

These still need double checking and final verification by species experts, but it’s a step in the right direction (and will be subject of yet another blog post from yours truly).

Secondly, we would absolutely love to feature invertebrates in the next Living Planet Index.

While this may not be quite achievable within the short time frame, we are about to start testing the feasibility of an LPI for butterflies, expanding from currently known European datasets and retrieving data for other well studied regions such as North America, and finally extending this to less-well studied regions, which are generally tropical areas.

Why might this be quite difficult? Because we need data on populations over time.

Many extinction risk assessments for invertebrates are based on much more basic data, especially locality data for species.

Extinction risk is then assessed by quantifying range extent and how this translates into the extinction risk metrics used by the IUCN.

Or, in a less long-winded explanation: we assess most inverts based on their range extent and evidence of decline, restriction or fragmentation within this range.

For the LPI, we need some counts or abundance measures to track trends over time.

For a population time series to qualify for the LPI, we need at least two years of data, from the same population, collected using the same technique to estimate population size or abundance. We’re confident there’s more data out there, but it takes time and effort to find it.

We also needn’t work alone – anyone with invertebrate abundance data fitting the requirements above could help us along by getting in touch with us.

The future

So watch this space and keep an eye out for butterflies featuring more prominently in future Living Planet Reports.

Hopefully this will be the beginning of a flurry of invertebrates fluttering, crawling, sliding and hopping their way into the Living Planet database!

Butterfly
The Indicators and Assessments Unit is currently coordinating the assessments of 1,500 randomly sampled butterflies or the Sampled Red List Index.

Learn more: The Living Planet Report 2016

 

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