|Believe it or not, this is a flying insect. So are most beetles.|
A study of 63 nature reserves in Germany involved trapping flying insects and weighing the biomass caught. Scientists and volunteers have been doing this since 1989, so they have a really good run of data. There was no attempt to identify the species caught, which would be very interesting too, but the numbers speak for themselves.
Over the last 27 years, their average catch has dropped by 76% meaning that they only have about a quarter of their insects left, but are still losing them at 6% a year, assuming that the decline is steady, which it probably isn't. I'm rubbish at maths but it doesn't look like we have very much time to turn this situation around.
Remember that this study was conducted in Germany which is a country that takes the environment very seriously. Despite being part of the same Common Agriculture Policy that we are, their countryside looks to me to be in much better shape than ours. Remember too that this was done on nature reserves, so the landscape as a whole would reflect an even worse situation.
|Many of our insects breed in water.|
The causes are really not known, but we can make guesses. If the country was a person, the reserves would be its liver. Nature reserves exist to produce a surplus of biodiversity, including insects and plants, that can spread out and (re) colonise the surrounding areas between reserves. We try really hard to do this but, what if the surrounding area is so toxic that they all fail to come home? Many bee species have declined by 30% in recent years and this is directly linked to pesticides on crops like oilseed rape that attract bees from miles around. Pesticides and pollution are certainly involved, but that's not the whole problem.
Imagine that you are an insect that only hatches when conditions are just right. The temperature and humidity are perfect, but your food plant is over, or has not yet flowered. "That's OK", you say, "I'll just fly upwind until I find my plant, or an alternative." But the (largely wild) plants that our insects evolved to live with (and evolved to live with them) are themselves in trouble. Take a look at a farm near you. How many "weeds" can you see? Those missing common wildflowers once fed our insects and their seeds fed our once-common birds like partridges, sparrows, buntings and finches. And that's farmland. Maybe the neighbourhood is now a new town with concrete parking bays, astro-turf yards and densely packed "town houses" with neither parking or gardens. It's impossible to argue that these changes haven't happened in the last 27 years, isn't it?
But here's another factor; climate change. If we just stay on our nature reserve where, on the surface, things haven't altered that much, we can see some pretty amazing changes such as very early springs and winters with no frost. Rivers no longer regularly flood in winter and lakes no longer freeze. Flowering dates may be all out of sync with the emergence of insects. And what about all the new species that are arriving? Many of them are predators like Asian hornets and harlequin ladybirds. There are new parasites too but these newcomers are a minor factor in my view.
The survey looked only at flying insects, many of which have their larval stage in water. We tend to think of a river or lake being a pretty stable environment, separate from the land around it, but of course it isn't. We have had acid rain, over abstraction, siltation, and eutrophication. If the main cause was to be pesticides, they would surely be in our waterways too, and where do we think all those medicines and chemicals go that we tip down the drain or the loo? A lot of upland rivers have never really recovered from pesticides used in sheep dips years ago and drainage of the uplands has created a rapid run-off situation which results in multiple short spates with droughts in between.
|Paxton Pits Nature Reserve. Looking good on the surface.|
Studies have been carried out over the years on many of our waterways and lakes to see changes in in the insect species that live there. Anglers have had concerns about this all of my lifetime ass the hatch of mayflies has all but disappeared in many rivers. I used to use a trout fly called the March Brown but the early season fly that it imitated is no longer around. Lakes and Lochs that once boasted prolific hatches of mayflies and caddisflies now only contain silt-loving midges that emerge in smothering swarms on summer evenings. Now it seems that even they are declining.
|Red Admiral Butterfly|
Moths are also in trouble. "Studies have found the overall number of moths has decreased by 28% since 1968. The situation is particularly bad in southern Britain, where moth numbers are down by 40%. Many individual species have declined dramatically in recent decades and over 60 became extinct in the 20th century." (Butterfly Conservation website)
I have worked on Nature Reserves for over 30 years and I studied butterflies and moths on Salisbury Plain in the 70s. I can tell you that insect decline is real and has arrived at a nature reserve near you.
The story get's worse. It's not only insects that are declining, on and off our reserves, insect eating birds are in trouble too. Shortage of insects in the breeding season means that chicks starve in the nest. The adults may only have a couple of years to reproduce themselves in and every failure contributes to a fall in the population. Is this what happened to our Nightingales? Swallows are declining across Europe, but seem to be stabilised in the UK. They are helped by having a long breeding season and may attempt to raise three or even four broods in a year, whereas many warblers only have one brood. Overall, our bird population is down 6% since 1970, but some species fare much worse than others.
This is from a Defra report this year (2017): "Birds associated with farmland, which covers 75 per cent of land in the UK, were down by 55 per cent, woodland birds by 21 per cent and seabirds by 20 per cent."
What can we do about all this? Certainly we must clean up our act and think Bug! When we manage a reserve, a farm or even a garden, we need to think about increasing the number of insects.