Though arthropods make up most of the species on Earth, and much of the planet’s biomass, they are significantly understudied compared to mammals, plants, birds, amphibians, reptiles and fish. Lack of baseline data makes insect abundance decline difficult to assess.

Insects in the temperate EU and U.S. are the world’s best studied, so it is here that scientists expect to detect precipitous declines first. A groundbreaking study published in October 2017 found that flying insects in 63 protected areas in Germany had declined by 75 percent in just 25 years.

The UK Butterfly Monitoring Scheme has a 43-year butterfly record, and over that time two-thirds of the nations’ species have decreased. Another recent paper found an 84 percent decline in butterflies in the Netherlands from 1890 to 2017. Still, EU researchers say far more data points are needed.

Neither the U.S. or Canada have conducted an in-depth study similar to that in Germany. But entomologists agree that major abundance declines are likely underway, and many are planning studies to detect population drops. Contributors to decline are climate change, pesticides and ecosystem destruction.

In recent months a debate over whether a global insect apocalypse is underway has raged in the mainstream media and among researchers. To assess the range of scientific opinion, Mongabay interviewed 24 entomologists and other scientists working on six continents, in more than a dozen countries, to better determine what we know, what we don’t, and, most importantly, what we should do about it.

This is part two of a four-part exclusive series by Mongabay senior contributor Jeremy Hance. Read Part I, “A global look at a deepening crisis” here.

Tyson Wepprich, a postdoctoral research associate at Oregon State University, was only supposed to be looking at the presence or absence of butterfly species in Ohio. But news of insect decline, in blockbuster studies from Germany and Puerto Rico, changed his plans. His team is now also looking hard at overall abundance — and the early results aren’t good.

“The trends are similar to those in long-term European butterfly monitoring where abundance, summed across all species, is declining at around 2 percent per year,” he says of the team’s unpublished work (Wepprich’s work is now published here), and “about twice as many species are declining rather than increasing.”

Wepprich’s ongoing research is just another sign that something may be seriously amiss with the world’s insects — something some entomologists have privately suspected, but which they are only now beginning to prove and publish about.

“I used to think of conservation as policies to save rare species from extinction,” Wepprich says, but adds he now believes conserving abundance must also be a part of any successful environmental strategy.

Insects: A conservation black hole

Despite the fact that arthropods make up most of the species on Earth, and much of the planet’s biomass, they are significantly understudied compared to mammals, plants, birds, amphibians, reptiles, fish and much else.

The IUCN Red List, for example, has assessed just 8,131 insect species regarding their extinction risk, a mere 0.8 percent of known insect species (the Red List estimates around a million insect species have been described). By contrast, the list has assessed 100 percent of all known mammals and birds. Moreover, today, nearly 300 years after Carl Linnaeus devised the system of taxonomy, we’ve only identified a small fraction of all the insect species inhabiting our world.

Conservation of insects, even of well-known species, has also lagged well behind conservation of other taxonomic groups. This is likely due to a philanthropic reality: it has proven far easier to raise funds for tigers, panda bears and whales than for glacier fleas, oleander hawk moths, or exploding ants. There are, of course, some conservation groups that focus solely on insects, like the Xerxes Society in the U.S., or Buglife in the U.K. But they’re far smaller and less well funded than those focused on big charismatic mammals or birds popular with the public. Millions of people call themselves “birders”; far fewer claim to be “insecters.”

In truth, for most of modern conservation history, environmentalists haven’t really worried much about insect conservation; the assumption has long been that if you protect umbrella species (also known as keystone or flagship species) in a landscape, you’ll be conserving all else as well. But new research by entomologists is clearly showing that’s no longer the case.