Why are insects in decline, and can we do anything about it?
The world’s insects are hurtling down the path to extinction, threatening a “catastrophic collapse of nature’s ecosystems”, according to the first global scientific review.
More than 40% of insect species are declining and a third are endangered, the analysis found. The rate of extinction is eight times faster than that of mammals, birds and reptiles. The total mass of insects is falling by a precipitous 2.5% a year, according to the best data available, suggesting they could vanish within a century.
Insect population collapses have recently been reported in Germany and Puerto Rico, but the review strongly indicates the crisis is global. The researchers set out their conclusions in unusually forceful terms for a peer-reviewed scientific paper: “The [insect] trends confirm that the sixth major extinction event is profoundly impacting [on] life forms on our planet.
“Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades,” they write. “The repercussions this will have for the planet’s ecosystems are catastrophic to say the least.”
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I walked my kids to school recently through the pretty North East English village of East Boldon and saw a red cross on a beautiful old rowan tree. I thought it might be the diesel haze of nearby commuter traffic confusing my senses, but no.
One email to my local councillors later and my worst fears were realised. The rowan tree, a species which feeds flocks of birds each autumn with its berries and whose only crime is to be old and gnarly, is for the chop – and the birds’ autumn lifeline with it.
In the email to my councillors I pointed out that two of the three trees slated for removal in that particular copse do not need to be cut down, they just need a bit of remedial work. One is a small tree smothered with ivy that simply needs to be stripped away.
The third is dead and I suggested in my email that the grounds team cut it into logs and scatter them around the small woodland – allowing them to rot for the benefit of fungi and insects, instead of their usual annihilation in an industrial grinder.
As a lecturer in ecology with 25 years of experience and over 30 peer reviewed papers published, I expected my suggestions to be taken seriously. While the councillor was prompt to reply and polite, it was made clear that grounds management is none of my business.
Clean and tidy is bad for wildlife
From my experience in the UK, grounds management teams employed by local councils seem unresponsive to expert advice. They also appear unsure how to reconcile having wild areas which are safe for human use but which remain useful for wildlife.
The small patches of wild and semi-wild areas in cities have been mostly stripped of their value to wildlife by over-intensive grounds management. Anything that has the vague look of irregularity is removed. No wood is allowed to lie on the ground, it must be tidied away. A 2013 report by the Royal Society for the Protection of Birds reviews the dramatic loss of wildlife habitat in the UK in great detail, emphasising the need to improve the semi-wild urban areas we still have for wildlife.
The wildlife value of a particular tree species in cities is often disregarded when a decision is made to remove it. In parks, plant species which are exotic to the UK such as the New Zealand cabbage tree (Cordyline australis) are intentionally planted because no native wildlife can use them, so they are low maintenance.
Pansies and other colourful flowering plants used in urban park borders are often useless for pollinators. This is due to modifications made during breeding of such plants which restricts access to the nectar producing organs and sometimes leads to lower rates of nectar production.
Petals of many ornamental plants are bred to enclose the central nectaries – nectar producing organs – and sexual parts of the flower that produce pollen and are of use to pollinators. This breeding gives the flower a beautiful ball shape but limits their use to insects. I suspect such plants are only put in urban parks in the first place to please the aesthetics of pensioners – a key voter demographic for local councils.
It doesn’t help that grounds management is often subcontracted to private firms in the UK. In these cases, grounds management is more likely to be insensitive to expert advice as the function is out of the hands of the democratically controlled body and with a private company that needn’t care what the public thinks.
Only a few UK councils that I am aware of are making progress in wildlife-sensitive grounds management. Councils such as Burnley, Dorset, Devon, Cornwall, East Sussex and Bristol have developed comprehensive pollinator action plans and are taking measures like allowing grass to grow longer in public areas, planting native, bee-friendly flowers and mowing verges less frequently.
The irony of it all is that measures to improve public areas for wildlife essentially involve less effort overall. All that really needs to be done is to allow public areas to be a little more unkempt, because unkempt areas are what nature likes. If local councils allow this to happen, the public shouldn’t berate them. We must be sympathetic to having natural and semi-natural areas that don’t look like Tellytubby land.
But I am sceptical. Local councils in the UK seem a long way from taking wildlife seriously. Unfortunately, the focus on human ideas of “neatness” at present dominates any love for nature. I fear that green spaces in urban areas will continue their decline as wildlife habitats.
Sir David Attenborough has told Prince William that people have never been more “out of touch” with the natural world than they are today.
In an interview with the prince at the World Economic Forum, the naturalist warned: “We can wreck it with ease, we can wreck it without even noticing.”
Sir David said people must care, respect and revere the natural world.
Heeding his words, the prince said: “Work to save the planet is probably going to largely happen on our watch”.
Sir David, 92, said: “When I started 60 years ago in the mid-50s, to be truthful, I don’t think there was anybody who thought that there was a danger that we might annihilate part of the natural world.”
In his early career, he said, simply showing people a new animal on television would astound them.
Even then, he added: “Television in Britain in the 50s was only seen by a few million people in southern England.”
Lake ecosystems make annual environmental changes more predictable. Nature conservation should not focus on individual species but on whole food webs, because the protection of their functioning is important for the predictability of species, especially when global warming is increasing environmental variability.
The environment varies drastically from year to year. Yet the variation of species in natural populations is positively correlated so that consecutive years tend to be fairly similar. Traditional population models cannot explain this phenomenon. Researchers have for long been wondering what the explanation could be, but they have now discovered a mechanism that translates various environmental variations into positive correlations in natural populations.
A new, more predictable food web model
A team of Finnish and US researchers used a food web model to simulate daily biomass development of plankton and fish species in Lake Constance. The model accounted for the prey-predator interactions and the age structure of fishes. The food web was subjected to environmental variation in terms of algal growth, that is, in the lake’s primary production. Such variation can be caused by annual changes in temperature, for example.
“This model differed from earlier ones, as it depicted a whole food web dynamics with 30 different species or age categories and altogether 133 prey-predator interaction links,” says Associate Professor Anna Kuparinen from the Department of Biological and Environmental Science in the University of Jyväskylä, Finland.