Feb 2023 Talk Reading the signs

February 2023 monthly talk
Reading the Signs - with entomologist Ray Barnett

Our speaker for February was one of our favourites, Ray Barnett, returning after an absence of several years. Ray has been based at Bristol Museum since 1989, and the Head of Collections and Archives for many years. Specialising in Entomology, Ray is also an all round passionate advocate for wildlife conservation.

“Reading the Signs” was subtitled: “What the bug life in our gardens reveals about our changing world.” In other words, studying invertebrate communities in our gardens, and seeing how they have changed over time, gives us clues and hard evidence about the effects of environmental change (in particular, climate change) on these communities.

There are an estimated 24 million gardens in the UK, covering 25% of the land surface. Not surprisingly, thousands of animal species live in, or visit gardens, including 45 of the UK’s priority species, for example, the stag beetle. To highlight this, in recent years, Ray has found in his urban garden the common field grasshopper, the lunar hornet moth and white-letter hairstreak butterfly, also a priority species.

Photo: Lunar Hornet Moth (Ian Kimber)

Ray outlined some of the changes in insect populations, many of which have increased in our area, among them the light brown apple moth, rose chafer beetle and garden tiger moth (which has replaced the cinnabar moth as the commonest red day-flying moth). Other notable successes include long-winged cone head, Roesel’s bush cricket, Box bug and Brassica bug. 2022 arrivals from the continent include the long-tailed blue butterfly, convolvulus hawk moth and crimson speckled tiger moth.

Photo: Rose Chafer beetle (Gail Hampshire)

Sadly, studies have shown many population decreases, and these butterflies have been lost from our area: the silver spotted skipper, wood white, black-veined white, mazarine blue, large tortoiseshell, silver-studded blue, Duke of Burgundy and pearl-bordered fritillary.

Ray suggested some of the main causes of insect population changes. Ironically, the first is an increase in predation by insectivorous bird populations, notably blue tits, which many of us feed and provide nest boxes for, to increase their population! Light pollution can affect moth behaviour and not just the adults; some larvae, which avoid coming out during the day to avoid predation, don’t feed at night because of increased light levels. Climate change, including bigger extremes of climate, has led to changes in population density and distribution. Species which overwinter as larvae are worst affected by unusually low temperatures.

Photo: Duke of Burgundy butterfly (Charlie Jackson)

Finally, two agricultural practices, the over-use of fertilisers and pesticides, are thought to have caused some serious declines in insect diversity. Studies show that 80% of butterfly species have decreased since the 1980s. We live in hope that more robust legislation against harmful farming practices is implemented more widely to halt and reverse these worrying declines.

Many thanks to Ray for his contribution to a very enjoyable evening.

Dave Sage