The huge decline in insect numbers has become a global issue. Scientists have announced that with the number of insects decreasing by 2.5% every year they could have disappeared completely in the next 100 years – their rate of extniction is 8 times faster than that of birds, mammals and reptiles in what the first Global Scientific Review has referred to as a “catastrophic collapse of nature’s ecosystems”.
To carry out this latest analysis 73 previously completed studies were selected to help assess the decline. As expected, butterflies, moths and bees were shown to have suffered extreme losses in numbers, with one study demonstrating that butterfly specieis fell by 58% on farmed land between 2000 and 2009 in England. A study conducted in the US found that only half of the bumblebee species recorded in Oklahoma in 1949 were still present in 2013, with the overall number of honeybee colonies in the US nearly halving in that time.
Beetle numbers are also declining at an astonishing rate, especially dung beetles. A study from the UK Environmental Change Network revealed a huge decline in the Carabid beetle in 2012. However, researchers have noted that there have been very little studies done around other insects such as types of flies, crickets, ants and aphids – but in their opinion there is no reason to expect that they are doing any better than the losses of those insects already identified.
The disappearence of insects would have a huge ecological impact; the main food source for many birds, reptiles, fish and amphibians, the loss of this food source could see starvation occur in many other species. Recently published research by Aberdeen University shows that the decline in the numbers of cuckoos in certain areas of the UK can be closely linked to the decline of the tiger moth caterpillers on which they feed. Insects also perform other crucial tasks such as helping to break down dead and rotting materials making way for new growth, helping weed control and providing raw materials for medicines.
What is causing this rapid decline? Unfortunately it is the same culprits that are cited time and time again; the increase in aggressive agrictulture and farming practices, climate change, and the increased use of pesticides. In this instance invasive species are also attributing to the decline; for example, thanks to the arrival of the Harlequin ladybird, at least 7 species of native ladybird have seen their numbers decrease including the two-spot ladybird who, when last assessed in 2012, had declined by 44%.
Steps can be taken to help increase insect numbers again; moth numbers have shown to increase in the UK where the planting of new trees has been underway. However, with many studies showing declining numbers even in nature reserves across the world, the issue is going to be much harder to resolve than simply planting more trees if some of the most protected habitats in the country are feeling the effects. There are also some species which have seen their numbers grow over the past few decades, but according to researchers these numbers are nowhere near enough to make up for the rate at which many are being lost.
Many are calling it an ‘Insect Armageddon’, although some researchers and journalists think that this terminology is a bit overkill and that the studies aren’t quite as cut and dry as they first appear. A research article published by Hallman, Sorg, Jongejans, Siepel, Hofland, Schwan et al., in 2017 called More than 75 percent decline over 27 years in total flying insect biomass in protected areas declared – well – that the total amount of flying insect biomass has decreased by 75%. However, it is worth taking a moment to consider the wording total flying insect biomass. In this study flying insects were caught in traps and then weighed, and it is the weight of those combined insects that has decreased, not the unique numbers of insects. According to Chris Shortall, an entomologist at Rothamstead Research, this is an important distinction – if two types of particularly large insect have declined, such as bees and beetles, this could skew the results to make the decline seem larger than it is. However 75% is a huge amount and it seems unlikely that this method of data collection has skewed the results so much that, if judged based on number of insects rather than weight, it would show no or little decline.
Another criticism of the accuracy of these reports is in the frequency at which surveys are conducted. Often years pass between surveys in specific locations, and many insects are known to work almost to a cycle in regards to their numbers dropping and the recouperating; until these surveys are carried out more regularly there is no being sure that this decline isn’t instead just a natural part of the insects cycle which will pick back up again.
Writing this I lost count of the number of studies I found over the past 20 years that showed how numbers of various insect types and species have been declining. Even with the valid criticisms with the way some of this research is carried out, there is too much, and showing too extreme levels of decline to deny there is any problem at all. It has now got to the stage where the best, and maybe only solutions are to decrease the amount of pesticides used, stop the sprawling urbanization and put more resources behing protecting our countryside, and to take a stand against aggressive agrucultural practices and those who think that climate change is ‘no big deal’. Unfortunately it’s a fight that many have been fighting for years, and whether anything will come of it before it is too late to save many of our species is questionable.
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