Moths are declining in the UK. 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. Sadly, among the species which have declined are many beautiful moths which were previously very common and frequently seen in our gardens.
These alarming decreases in moth populations are not just bad news for the moths themselves, but also have worrying implications for the rest of our wildlife. Moths and their caterpillars are important food items for many other species, including amphibians, small mammals, bats and many bird species. Moth caterpillars are especially important for feeding young chicks, including those of most familiar garden birds such as the Blue Tit and Great Tit, Robin, Wren and Blackbird. A serious decline in moth numbers could have disastrous knock-on effects for all these wildlife species. Already, research has indicated that a decrease in the abundance of bats over farmland is related to the decline in the moths that they depend on. Cuckoos may also have been affected. They specialise in eating hairy caterpillars, which most other birds avoid, and it has been suggested that the drop in our Cuckoo population may be linked to the decline in moth caterpillars like those of the Garden Tiger.
It is not clear what is causing the downward trend in our moth numbers. The reasons for the loss of moths are likely to be many and complex, and may vary for different species. More research is needed to understand what is happening. However, the loss of habitats resulting from more intensive agriculture, commercial forestry, industry and urban development are likely to be major reasons.
Other things which may be causing problems for moths include changes in the way we manage our gardens, pesticides, herbicides and light pollution. Climate change is also affecting moths. Whatever the causes, the decrease in moth numbers is a warning to us that all is not well with our environment.
Although many people overlook them, moths are numerous and widespread, with over 2,500 species in Britain living in a wide range of habitats. They are a major part of our biodiversity and play vital roles in the ecosystem, affecting many other types of wildlife.
Both adult moths and their caterpillars are food for a wide variety of wildlife, including other insects, spiders, frogs, toads, lizards, shrews, hedgehogs, bats and birds. Night-flying adult moths form a major part of the diet of bats. Many birds eat both adult moths and their caterpillars, but the caterpillars are especially important for feeding the young. Some of Britain's favourite garden birds rely on caterpillars to rear their nestlings, with our blue tit chicks alone needing an estimated 35 billion a year!
Moths also play a vital role in telling us about the health of our environment, like the canary in the coalmine. Since they are so widespread and found in so many different habitats, and are so sensitive to changes, moths are particularly useful as indicator species. Monitoring their numbers and ranges can give us vital clues to changes in our own environment, such as the effects of new farming practices, pesticides, air pollution and climate change. Moth caterpillars have a great impact on plants by eating their leaves.
This had led to many types of plant evolving special chemicals to make them less appealing to caterpillars and limit the damage. But moths also benefit plants by pollinating flowers while feeding on their nectar, and so help in seed production. This not only benefits wild plants but also many of our food crops, which depend on moths as well as other insects to ensure a good harvest.
Why butterflies and moths are important
There are many reasons why butterflies and moths are important, both in their own right but also as quality of life indicators. The following are the main reasons for conserving butterflies and moths in the UK and around the world.
- Butterflies and moths are intrinsically valuable and are worthy of conservation in their own right.
- Butterflies and moths are part of Life on Earth and an important component of its rich biodiversity.
- They have been around for at least 50 million years and probably first evolved some 150 million years ago.
- Butterflies and moths are a highly diverse group comprising over 250,000 species and make up around one quarter of all named species.
- Butterflies are flagship species for conservation in general, and in particular for invertebrates.
- Butterflies and moths are part of our natural heritage and have been studied for over 300 years.
- Butterflies and moths are beautiful. Many are iconic and popular.
- People like butterflies.
- There are many references to butterflies and moths in literature, from the Bible through Shakespeare to modern day literature, and from poetry to musical lyrics.
- Butterflies are used by advertisers and illustrators the world over as way of indicating that something is environmentally friendly.
- Butterflies are often portrayed as the essence of nature or as representing freedom, beauty or peace.
- Butterflies and moths have fascinating life-cycles that are used in many countries to teach children about the natural world. The transformation from egg to caterpillar to chrysalis is one of the wonders of nature.
- Other educational aspects include the intricate wing patterns and iridescence, and as examples of insect migration.
- Butterflies (and moths to a lesser extent) are an extremely important group of ‘model’ organisms used, for centuries, to investigate many areas of biological research, including such diverse fields as navigation, pest control, embryology, mimicry, evolution, genetics, population dynamics and biodiversity conservation.
- The long history and popularity of butterfly study have provided a unique data resource on an insect group unmatched in geographical scale and timescale anywhere in the world. This has proved extremely important for scientific research on climate change.
- Butterflies and moths are indicators of a healthy environment and healthy ecosystems.
- They indicate a wide range of other invertebrates, which comprise over two-thirds of all species.
- Areas rich in butterflies and moths are rich in other invertebrates. These collectively provide a wide range of environmental benefits, including pollination and natural pest control.
- Moths and butterflies are an important element of the food chain and are prey for birds, bats and other insectivorous animals (for example, in Britain and Ireland, Blue Tits eat an estimated 50 billion moth caterpillars each year).
- Butterflies and moths support a range of other predators and parasites, many of which are specific to individual species, or groups of species.
- Butterflies have been widely used by ecologists as model organisms to study the impact of habitat loss and fragmentation, and climate change.
- People enjoy seeing butterflies both around their homes and in the countryside.
- Over 10,000 people record butterflies and moths in the UK alone, involving getting outside and walking considerable distances. Over 850 sites are monitored each week in the UK and collectively volunteers have walked the equivalent of the distance to the moon counting butterflies.
- Several hundreds of thousands of people garden for wildlife in the UK, many of them specifically for butterflies and moths.
- Thousands of people travel abroad each year looking for butterflies and moths. Eco-tours bring valuable income to many European countries and developing countries around the world (e.g. the valley of the butterflies in Rhodes and the Monarch roost in Mexico).
- Every butterfly and moth has developed its own suite of chemicals to deter predators and parasites, find a mate, and overcome the chemical defences of its host plant. Each of these chemicals has a potential value and could be exploited economically.