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Research shows land insect numbers are falling and putting the world’s ecosystems at risk

April 26, 2020 6:02AM Reuters

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Butteflies, which give humans much joy with their beauty, are among the land-dwelling insects experiencing a drop in numbers. media_cameraButteflies, which give humans much joy with their beauty, are among the land-dwelling insects experiencing a drop in numbers.

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The world has lost more than one-quarter of its land-dwelling* insects — such as ants, bees, butterflies, grasshoppers and fireflies — in the past 30 years, but freshwater bugs such as dragonflies and mosquitoes have been rallying*, researchers have revealed.

The findings were based on 166 sets of data* on more than 10,000 species from 1676 sites in 41 countries dating as far back as 1925.

“The decline across insect orders on land is jaw-dropping*,” said Michigan State University butterfly expert Nick Haddad, who wasn’t part of the study. “Ongoing decline on land at this rate will be catastrophic* for ecological systems and for humans,” he said.

media_cameraGrasshoppers are among the land-dwelling insects whose numbers have dropped.

The figures showed the drop in land insect numbers was 27 per cent in 30 years.

However, insects such as mosquitoes — which live in the water as larvae — as well as midges, mayflies, water beetles and caddisflies that spend at least part of their lives in freshwater, were found to have experienced a population increase of about 11 per cent per decade.

Freshwater covers only about 2.5 per cent of the Earth’s surface, so the majority of insects live on land.

The number of insects on average has declined in the air, in the grass and on the soil surface, but not in trees or underground, the researchers found.

What on Earth would survive a nuclear war?

Projecting the trends into the future shows that land-dwelling insects would experience a population drop of 24 per cent over the next 30 years while the freshwater bugs would have a 38 per cent increase over the same period.

“Insects are a central part of almost all ecosystems* because they stand in the middle between the plants they eat and the animals that eat insects, like birds, bats and lizards,” said entomologist* Roel van Klink, who was the lead author of the research published in the journal Science.

“They also impact our own lives, often in ways we don’t think about. Insects pollinate* many of our crops, and without them, we would have no fruits and no flowers. But at the same time, insects transmit terrible diseases like malaria, Zika and West Nile virus, they eat our crops and damage tree plantations,” said van Klink, who works at the German Centre for Integrative Biodiversity* Research.

Feeding mosquito media_cameraMosquitoes and other freshwater bugs have seen an increase in numbers.

The study did not break down the findings by species*.

It did find that the strongest declines were in the midwest of the United States and in Germany.

There was very little data from South Asia and the Middle East, and limited data from Africa.

The researchers praised clean-water policies introduced in recent decades for the increase in freshwater bugs.

They blamed the declines in land-dwelling insects to human activities such as habitat destruction and building more towns and cities on farmland as well as light pollution and chemical pollution.

The researchers said the use of insecticides* and drought may have also played a role.

GLOSSARY

  • land-dwelling: live on land
  • rallying: improving
  • data: information or evidence
  • jaw-dropping: surprising
  • catastrophic: disastrous
  • ecosystems: all of the living and non-living things in an area
  • entomologist: a person who studies insects
  • pollinate: the process that allows plants to grow new plants
  • biodiversity: the variety of living things in one place
  • species: a group of similar living things
  • insecticides: poisons designed to kill insects

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QUICK QUIZ

  1. What percentage of land insects are being lost each decade?
  2. The research studied how many species?
  3. When did the research project begin?
  4. How much will freshwater bug numbers increase in the next 30 years?
  5. Name three reasons why land insect numbers are dropping.

LISTEN TO THIS STORY


CLASSROOM ACTIVITIES
1. Building scientific knowledge
There are lots of numbers and percentages in this story – often these types of figures are easier to understand when they are presented visually as graphs.

Choose one piece of data that is presented in the story, decide what type of graph would best visually represent that information and create the graph. You can choose to make your graph manually (by writing/drawing on paper) or digitally (by entering the data into a computer program such as Microsoft Excel and generating a graph).

Time: allow 30 minutes to complete this activity
Curriculum Links: English; Mathematics; ICT Capability


2. Extension
Get out in the garden or schoolyard and collect some raw insect data of your own. Keep a record of the first 50 insects you can find. Create a graph or visual to represent the data from your results.

Time: allow 20 minutes to complete this activity
Curriculum Links: English; Mathematics

VCOP ACTIVITY
The glossary of terms helps you to understand and learn the ambitious vocabulary being used in the article. Can you use the words outlined in the glossary to create new sentences? Challenge yourself to include other VCOP (vocabulary, connectives, openers, and punctuation) elements in your sentence/s. Have another look through the article, can you find any other Wow Words not outlined in the glossary?

HAVE YOUR SAY: What is your favourite or least favourite type of insect?
No one-word answers. Use full sentences to explain your thinking. No comments will show until approved by editors.

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