The Life of the River: Celebrating Insects
This National Insect Week, we’re celebrating all of the entomological wonders freshwater ecosystems have to offer. Today, we hear from Jenny Pearson—Rivers Trust Ambassador. If you have ever enjoyed watching dragonflies flit across the water, or marvelled at birds swooping to catch mayflies on the banks, please do consider making a donation. With your help, we can make our dream a reality: wild, healthy, natural rivers valued by all.
If you are interested in becoming an Ambassador for The Rivers Trust, please head over to our Ambassador page for more information.
Late into the longest day of the year, the summer solstice, the sun is low in the late evening sky casting an orange glow over the cool June air. Golden speckles flutter like fairy dust over the surface of the water as the sun dances against adult mayflies searching for a mate before being grabbed by a swooping sand martin. All around, the evening is filled with the buzz of white-tailed bumblebees collecting the last of the days nectar from the wildflowers that grow in great densities along the bank of the river, and whistling crickets amongst the long grass. On the wood of the overhanging willow, an emperor dragonfly slowly emerges from its nymphal case, hanging its delicate wings out to stiffen in the warm air. A fluttering flash of orange, an orange tip speeds past, hovering over several plants before coming to rest on a tall, white Dame’s Rocket.
With six legs, paired wings and three body parts, you might think I have just described a green skinny comic book alien from another unimaginable world, but all I have in fact described is a group of creatures that make up more than half of the worlds biological diversity, a group of creatures that rule our world, a group of creatures with whom our lives are inextricably dependent upon – insects. Insects are the most diverse group of animals in the existence, they come in multiple forms – butterflies, flies, bugs and beetles, wasps and bees, (my personal favourite) dragonflies, and many more. Creeping, fluttering, flying beasties, they bring colour and drama to our world that is beyond imagination. Some people are turned off by insects, unsettled by their creeping, flickering nature. But insects are something to be enjoyed and to be celebrated, and it just so happens that this week marks National Insect Week!
In the past 150 years, farming practices have given insects a hard time; toxic chemicals became common practice in attempt to improve crop quantity and quality. Instead, an ecological disaster occurred. Indiscriminate chemicals destroyed insect populations, and as the food source of many larger vertebrates, frogs and bats and birds for example, other wildlife populations crashed as a result. Habitat change, changing climates and other forms of pollution are putting a great strain on our world’s insect populations. Insects are key to healthy, thriving and sustainable ecosystems. We all know the importance of the bees – without bees and other pollinators, our food production systems would collapse, and humanity would likely be plunged into famine. But what about the other creepy crawlies? And what can insects tell us about the health of a river system?
Ecosystems are complex, and where 50% or more of an ecosystem is made up of insects, the loss of these creepy crawlies could lead to disastrous ecosystem collapse. An abundance of insects feeds an abundance of larger, perhaps more charismatic species. Where there are insects in rivers, fish and amphibians can feed and thrive. And where there are fish, animals that are widely adored such as otters, and magnificent bird species, such as Grey Herons, Egrets and King Fishers can inhabit these areas (perhaps even Ospreys!).
Insects act as indicator species, with short life-spans, small body sizes, specific food requirements and very sensitive to changes in oxygen and chemical levels in the water, many insects are very intolerant to pollution and populations respond to pollution very quickly. Important prey items such as Mayflies, Stoneflies and Caddisflies are highly intolerant to pollution and populations quickly disappear, followed by a crash in the population of their predators. The presence of these insects can indicate a healthy, thriving river ecosystem! Dragonflies and Damselflies spend their entire nymphal stage under the water feeding and growing (this can last 1 or many years depending on the species) are slightly more tolerant to levels of pollution and so may be able to exist in areas where pollution levels are moderate, indicating a semi-healthy river. A heavily polluted river is likely to lack all of these fantastic creatures and the great animals that feast upon them. Some insects are able to tolerate these waters (such as the infamous midge) and a high presence of these insects and a lack of others, is likely to indicate a highly polluted water system.
So next time that you are sat by a river, watching a heron stalk its next meal, or listening out for bird song, or watching bats swoop through the air, or fishing for trout. Take a moment to appreciate the insect life around you – look out for the weird beetles, wacky bugs, striking dragonflies. These insects breathe life into the rivers, they are the true soul of the party. Without insects, rivers would bleak and lack the magic that they do. Take the time to get to know them, enjoy them, celebrate them, like every other endangered species, insects need our time and support.