It was alarming to read recently of the decline in populations of flying insects in Europe. Studies in Germany alone has seen a reduction 76% since 1989 in nature reserves. The reasons for the die off are thought to be manifold. Although the exact cause of the die off is not known, amongst the theories are an increase in the use of nitrogen fertiliser as well as the over use of pesticides. Loss of habitat is probably also a factor. Not only is this a reduction in pollinating insects but also the loss of a valuable food source for many animals especially birds.
In recent times Europe has also seen a reduction in bird numbers. In the USA it is estimated that wild insects contribute $57 billion to the economy due to their role in the ecosystem and as pollinators. It is important to consider the role of insects in your garden both as pollinators and in attracting birdlife keeping in mind the fact that many of the insects in your garden have a direct or indirect benefit to your plants.
In urban environments, as well as rural and semi rural, domestic gardens have been identified as important habitats for animals and especially insect diversity. Domestic gardens are a large proportion of land use in urban areas and contribute greatly to urban green space. Gardens and other urban green spaces , as well as providing valuable ecosystems, also help with habitat, cooling, flood mitigation, and support human health and well-being.
There is no doubt that the main driver for plant selection in the urban gardens is the attractiveness and aesthetic appeal of plants and flowers. Flowering plants also provide valuable food resources including both nectar and pollen for invertebrate insects as well as birds and mammals. Some of these animals might, but not necessarily, pollinate the plant. Most of the flying insects, not just bees, that visit flowers are potential pollinators.
Scientific studies in the UK have shown that gardeners can support pollinating insects in gardens by planting a mix of flowering plants from different regions. This might not be the case in Australia with its unique ecosystems, but in some cases using a mix of plants may give your garden a steady supply of flowering plants all year round.
Studies also found that in the United Kingdom with its short summers, the more flowers a garden can offer throughout the year, the greater the number of bees, and other pollinating insects it will attract and support.This was regardless of whether the plant was native or non-native. In South East Queensland, it is probably better to select a higher quantity of indigenous plants and smaller numbers of exotic plants for colour contrast. The Australian native plants tend to have more drought tolerance than exotic species. A densely planted flowering garden with a variety of local and exotic flowering plants will provide both food and habitat for insects and small animals.
Non pollinating Insects
Are non-pollinating insects also important in the garden? The invertebrates in your garden are either predators, omnivores, herbivores or detritivores. The detritivores play an important role in your garden as they are animals which feed on dead organic material helping to break it down to feed the plants. The benefits of insects to your top soil should not be underestimated.
The predators, like the lady bird but also including other beetles, along with ants, wasps and spiders, help to control some of the garden pests. Potential prey for ladybirds include aphids (Hemiptera: Aphididae), coccids, pseudococcids, and diaspidids ( Hemiptera: Coccoidea), whiteflies (Aleyrodidae).
Coccinellidae, ladybug lady bird or lady beetle. This carnivorous insect loves to fest on your garden pests such as aphids and scale insects. It even lays its eggs in the pest insect colonies. They are sometimes used for controlling pests in greenhouses. Where possible, aphids should be controlled by using the garden hose rather than insecticide. Any insecticide spray used on aphids will probably harm your ladybirds as well.
Other insects in your garden will attract birdlife, so consider planting at least part of your garden with insects and animals in mind.
For more information on wildlife in the garden see our blog http://redslandscaping.com.au/wildlife-in-the-garden/
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References and further reading.