How native plants are essential for pollinator and ecosystem health
© Claire O’Neill (Earthwise Aware)
Biodiversity loss
According to recent reports, including from the climate and biodiversity scientists at the UN, climate change and biodiversity loss are equally threatening to human existence. Around the world, one million species are diminishing in numbers and face extinction, many within decades. In the US, 34% of plant species, 40% of animal species, and 41% of ecosystems are at risk of extinction.
In North America we have lost 30% of our birds since 1970 – almost 3 billion birds. A major reason for this decline is the loss of a critical food source for birds and their young: insects. Insect populations are falling so rapidly that unless we take action to reverse this trend, they could be gone by the end of the century. In Massachusetts we have almost 400 native bee species, many declining in number. (This does not include honeybees, which are not native to our continent and are not at risk as a species.)
The EO Wilson quote above might sound surprising, since many of us are brought up to view insects as dangerous, disgusting or insignificant. In fact, insects are essential for the healthy functioning of all ecosystems.
The importance of insects
Insects pollinate many of our food crops: without insects, we have no fresh fruits and vegetables. They pollinate 90% of our flowering plants: without insects, most plants can’t reproduce. Insects are food for many species, and in turn, the species that eat insects are food for others. Insects are an essential part of the entire food web.
What are the causes of this alarming and dramatic decline in insect populations? The widespread use of pesticides, herbicides and chemical fertilizers; the increase in invasive plants and insects; light pollution; and climate change all have detrimental impacts on insect populations, but habitat loss is the greatest cause. Industrial agriculture, urbanization, and deforestation all contribute to the loss of habitat. Another important aspect of habitat loss is the widespread use of non native plants. We will explain why this is so – and the good news is, we can all take action to reverse this trend.
Native plants are essential to the life cycle of insects (and other species)
Insects and plants have been co-evolving for 125 million years. Plants depend on insects for reproduction, and insects depend on plants for food, both for adult insects and for their offspring. Plants defend themselves from excessive feeding with several mechanisms, one of which is the production of chemicals that make them unpalatable or toxic to insects. Insects have evolved enzymes that enable them to bypass the toxicity of these chemicals – but only for certain species of plants.
The result is highly specialized relationships between insects and plants. 90% of insects can only feed themselves or their offspring on one or two species of plants. Most plants can only be pollinated by limited species of insects. Plants and insects have co-evolved to have very specific (and fascinating) symbiotic traits that enable them to have mutually beneficial relationships. Most imported plants do not offer these benefits to local insects, since they evolved in other ecoregions with different insects. The traits of hybridized plants are often changed in ways that remove or lessen their ability to feed insects. Thus native plants are needed to feed insects and their young – insects which will pollinate plants, enabling them to reproduce; and will themselves be food for many other species, including birds.
What can we do?
We can reverse the trend towards species extinction by putting native plants in our landscapes and using ecological landscaping practices that provide protection, food, and shelter to insects throughout their life cycles and the year. By planting native plants, we get the joy of creating beautiful gardens and landscapes that are teeming with life.