What have insects ever done for us?

From pretty butterflies to pesky mosquitoes — insects are among the most diverse and dominant groups on earth. Nearly 1 million species are known to exist and there are likely many more to be discovered. According to a UN biodiversity study, up to 40% of insects species are threatened with extinction in some parts of the world. Many people do not realize that their loss would be keenly felt.

Crops, such as wheat, are wind pollinated, but many other food crops depend on insects for pollination. Their disappearance would come at great cost to farmers. Some $235 billion of yearly global food production relies on pollinators. In some farms in China, workers are hand-pollinating apple and pear trees because of the lack of bees. Such labor-intensive work pushes up food prices.

Pollinator disappearance also means we'd lack much of the fruit and vegetables we eat — and we wouldn't be enjoying beloved treats like chocolate and coffee. Apart from food, pollinators also contribute to the fibers, such as cotton, from which we make our clothes, as well as to plants on which certain medicines are based.

Many insects, like the dung beetle pictured here, decompose dead plant matter, carrion and feces that would otherwise be left to decay in our environment. Basically, the world would be a smellier and less hygienic place without them.

Insects are the main source of food for many other animals, including amphibians, reptiles, certain mammals, and birds. And as insects disappear, there could be declines in the species that feed on them too. Ornithologists believe sharp declines in bird species in the UK, for instance, are at least partly linked to a drop in insect numbers.

Climate change is also affecting insects that are slow to adapt. Bumblebees for instance are suited to cool and wet climates and may find it difficult in warmer weather. But insects that are pests are already spreading to new habitats. The European corn borer (pictured), which can destroy corn harvests, is among them. That means farmers use more pesticides that kill pollinating insects.

Intensive farming is one of the major factors behind insect declines in Europe. Fertilizers, pesticides and insecticides are all driving the decline, as are monocultures — the practise of growing of a single crop or plant. That takes refuge and habitat, like diverse flowering meadows, away from insects.

Experts say a more insect-friendly farming policy that relies less on pesticides and monocultures would boost their numbers. But planting blooming flowers in gardens and urban areas would also provide food and habitat for bumblebees and butterflies. Another option is building more "insect hotels," (pictured) for solitary critters, like leafcutter bees, which like to nest in tunnels.