Скачать или смотреть The Great Thinning | Insects - April 25, 2019

The Great Thinning | Insects - April 25, 2019

For several years, ecologists and biologists have been concerned about losses in the biodiversity of terrestrial and aquatic vertebrates.
However, scientists are now starting to show greater concern over the dramatic declines of invertebrate taxa, particularly insects (1).

A recent publication, Worldwide decline of the entomofauna: A review of its drivers, reveals dramatic rates of decline that scientists say may lead to the extinction of 40% of the world's insect species over the next few decades.
The study published in journal Biological Conservation reviews 73 historical reports of insect declines from across the globe, and systematically assess the underlying drivers.

“From our compilation of published scientific reports, we estimate the current proportion of insect species in decline (41%) to be twice as high as that of vertebrates,” the scientists say (1).
They estimate the pace of local species extinction (10%) is eight times higher than that of vertebrates, confirming previous findings (1).

At present, about a third of all insect species are threatened with extinction in the countries studied.
“Moreover, every year about 1% of all insect species are added to the list, with such biodiversity declines resulting in an annual 2.5% loss of biomass worldwide (1).”

In the US, changes in the distribution of eight bumblebee species were determined by comparing historical records with intensive survey across 382 locations.
“Half of the species declined in abundance by as much as 96% of their initial populations only in the last 30 years, and their geographical range was reduced between 23 and 87% (1).”
“In the USA, a peak of six million honey bee colonies was recorded in 1947 but this number has been declining ever since.”
The reduction to the number of honey bee colonies is “3.5 million over the past six decades at a 0.9% annual rate of decline (1).”
“Two thirds of American beekeepers presently lose about 40% of their colonies every year. (1)”

The main drivers of worldwide species declines, in order of importance, seem to be:
habitat loss and conversion to intensive agriculture and urbanization;
pollution, mainly that by synthetic pesticides and fertilizers;
biological factors, including pathogens and introduced species;
and climate change.

The primary factors responsible for declines in honey bee colonies include:
i) widespread parasite and pathogen infections;
ii) toxic pesticide residues found in the pollen and nectar or applied to hives for controlling Varroa mites;
iii) and poor nutritional value of agro-landscapes dominated by monocultures;

Agricultural supply chains face many non-uniform and presently unidentified risks due to these declining numbers of insects.
This is because many invertebrates are pollinators, which are directly linked to agricultural production.
Pollination directly affects the yields and/or quality of 75% of globally important crops, and the proportion of global agricultural production that depends on pollinators has increased four- fold since 1961 (2).
But over 16% of vertebrate pollinators are threatened with global extinction, 9 per cent of wild bee and butterfly species face local extinction, and available National Red Lists show up to 50 per cent of bee species assessed are nationally threatened (2).

Steps to mitigate the insect apocalypse are relatively straightforward.
“Habitat restoration, coupled with a drastic reduction in agro-chemical inputs and agricultural ‘redesign’ is probably the most effective way to stop further declines, particularly in areas under intensive agriculture (1).”

Quelling losses to the population of pollinators includes:
i) raising pesticide regulatory standards to incentivize best practice use of pesticides and reduced exposure of pollinators;
ii) reducing overall use of pesticides, through integrated pest management (IPM);
iii) and raising standards of risk assessment of genetically modified crops worldwide (2).

In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments (1).

Because the annual contribution of pollinators to the global economy is estimated at US$ 235–577 billion (2), society would be wise to consider the current state.

Image source: MrMBB333, https://www.mrmbb333.com/.

Sources:
1.Worldwide decline of the entomofauna: A review of its drivers, Biological Conservation.
2.The pollination Deficit, Cambridge Conservation Initiative (CCI).