Where have all the insects gone? 

A recent radio piece caught my attention, describing a German study which documented dramatic declines (80%) over the past 30 years in the number of flying insects present in nature preserves. (Read it for yourself here  

Why we care 

These insects include many that are important pollinators of food crops and wild plants, and are therefore key to human food systems and to the ecosystems they inhabit. Insects are also the foundation of the animal food chain. Songbirds, which rely on insect protein for a huge portion of their diets, are in decline in both Europe and North America, and this loss of insect food sources is almost certain to play a part.  

 Researchers have not pinpointed the cause of the insect decline, but the two leading suspects are habitat loss and pesticide use in the surrounding areas. Interestingly, these are both conditions that Landscape Architects, gardeners, and any consumer of landscape design can influence.  

 Problem 1 – Habitat Loss, and how we can help 

The first suspect in the declining insect population is insect habitat loss.  Areas in and around the nature preserves have become more intensely converted into agricultural use.  Insects need a broad range of (mostly native) flowering plants throughout the year to maintain a breeding population, which a field of wheat or potatoes simply does not provide. That any field is exclusively planted in one or very few crops means that insects have few food options. This problem exists anywhere that complex native plant communities have been eliminated, which means that urban, suburban, and agricultural regions have all become insect food deserts. (See our blog post here for a discussion of why native plants specifically are so important to regional biodiversity). 

 As designers, whether we are working in urban, suburban, or rural contexts, it is crucial to integrate insect habitat wherever possible. While this can be as simple as providing a variety of native plants within the design, it does require care and intention to pull off well.

The High Line in New York City is a prominent example on this continent of how naturalized and native plant communities can be successfully integrated into a highly urban and heavily used space.

In a suburban landscape, a typical ornamental yard can be specifically designed to include a critical mass of native plants, as was done in this project, situated in the Raleigh Hills neighborhood of SW Portland.  

Native wildflowers in this suburban wet meadow provide food for pollinators.

Problem 2 – Insecticides, and how we can help 

The second prime suspect is the use of pesticides, especially the neonicotinoid class of chemicals, which are used in both food production and the nursery trades. Neonicotinoids are especially pernicious because the chemical remains present in plant tissue long after treatment, harming insects that were not the original target. This means that a flower we plant may actually be poisoning the bees and butterflies that we are trying to help, because it was treated as a seed or seedling. As awareness of this problem grows, it is now possible for consumers and landscape architects to choose plants from nurseries that do not use these compounds. Local Portland nursery Garden Fever makes it especially easy for gardeners by specifically labeling plants as “Pollinator Safe.”  See here for a national scale list of insect friendly retailers and wholesalers in the US. Please consider this next time you go garden shopping! 

 Of course, we all eat food, so this is also a time to remember the benefits of sustainable agriculture. Choosing to buy organic food may not solve all the world’s woes, but it is one way to support agricultural practices which do not expose the surrounding people, land and animals to chemical harm.  

 

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