Nova Scotia·sharing our planet

Why some of Nova Scotia's smallest animals are in decline

Insect biomass is dropping across the globe, including in Nova Scotia, where certain species — such as the yellow-banded bumblebee — are in steep decline.

Habitat loss, introduced species and pesticides are all contributing factors

The Monarch butterfly is listed as endangered in Nova Scotia. (Alain Belliveau)

This is the third in a series of stories from CBC's Information Morning Nova Scotia about species that are struggling to survive in Nova Scotia, and the people who have vowed to save them. 

Bug-splattered windshields were once a staple of summer road trips across the province. But in recent years, windshields aren't getting as dirty — and that's a bad sign for insects. 

"There is good reason to believe that the overall biomass of insects, or just the sheer number of insects in the environment, has declined," said John Klymko, zoologist at the Atlantic Canada Conservation Data Centre.

The yellow-banded bumblebee is one of the insect species in decline in Nova Scotia. (John Klymko)

Klymko said there isn't enough background data to say definitively how all insect species are doing. But anecdotal evidence — like the decline of bug splatter on windshields — as well as studies conducted elsewhere paint a bleak picture.

One German study which trapped flying insects over a 27-year period found a 76 per cent drop in the biomass of the insects caught.

"They weighed the samples from 27 years ago, and compared them to the samples now... They were much less than what we were catching in the past." 

Some species in steep decline

In Nova Scotia, there are also a number of insect species that are in decline.

"There's one species called the yellow-banded bumblebee, which is still a widespread species. It's found throughout the Maritimes. However its abundance is nothing like what it used to be 30 years ago."

In decades past, 30 percent of bees in a field would have been yellow-banded bumblebees. Now, that number is down to about four percent, and it isn't the only species of bee that's in trouble.

The gyspy cuckoo bumblebee, which invades the nests of bumblebees and uses them to raise their own young, is only known from the historical record in Nova Scotia, and is endangered elsewhere in the country.

"The gypsy cuckoo bumblebee is thought to have used yellow-banded bumblebee as its primary host, so you can imagine if the host has declined significantly, then those cuckoos... might not be able to survive such a decline."​

Klymko said habitat loss and introduced species are driving the decline in insects. 

Yellow-banded bumblebees, for instance, may be affected by pathogens that are hitching a ride on species like the eastern bumblebee, which was first domesticated in Europe and is commonly used in agriculture as a pollinator.

"It's thought that perhaps when those bumblebees were brought to North America they brought back diseases...that some of our native bumblebees like the yellow-banded are especially sensitive to."

A cascade effect

The pesticides used in agriculture could also be contributing to the drop in insect populations, Klymko said, by making insects less productive and causing them to have fewer offspring. 

As species decline, this isn't just bad for bugs. There will be a whole cascade of effects for animals from fish to birds, said Klymko.

But people can help address the issue by becoming more familiar with our natural environment, Klymko said, and thereby maybe finding a way to save it. 

Read more from this series: 

With files from CBC's Information Morning Nova Scotia

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