Designing Landscapes for Insects

Insects and other invertebrates account for over 90% of all living species, building the basis for most ecosystems. In fact, they often dominate their landscapes through both sheer number and volume, providing many key services, either directly or obliquely, as pollinators, recyclers, pest control and as food for a host of animals.

Keeping this in mind, the responsibilities of the modern design practitioner are more challenging than ever before. Due to the effects of climate change, habitat loss, and pesticides, insect populations are declining worldwide. Honeybees, for example, have attracted media attention since 2006, with their death tolls linked to neonicotinoids, colony collapse disorder, and a lack of supportive flora.

Honey bee pollinating Butterfly Weed (Asclepias tuberosa), the larval host of the Monarch and Queen butterflies, 2015. Copyright: Ansel Oommen

Honey bee pollinating Butterfly Weed (Asclepias tuberosa), the larval host of the Monarch and Queen butterflies, 2015. Copyright: Ansel Oommen

The monarch butterfly, whose population once reached 900 million in 1995, now sits precariously at a meager 56.5 million- a 95% drop, placing it within risk of extinction.

Underlying the struggle of invertebrate conservation is a pervasive negative image. Mislabeled as “creepy crawlies”, many bugs, even beneficial ones, can elicit common phobias, further hindering public support and activism.

However, as biologist E.O. Wilson summarized, “If we were to wipe out insects alone, just that group alone from this planet, which we are trying hard to do, the rest of life and humanity with it would most likely disappear from the land- and within a few months.”

So while they are not the top priority in the urban environment, we must reconsider these multi-legged critters as allies in our future narrative. This calls for direct collaboration between entomologists and design professionals. Because insects have multiple life stages with shifting needs, ecological site design is best developed with seasonal and generational changes in mind. Many species including wasps, beetles, flies, and moths, for instance, are marked by a semi-mobile larval stage, an immobile pupal stage, and a highly mobile adult stage, requiring a scientific understanding of their habitat preferences.

Each of these stages of the Black Swallowtail (Papilio polyxenes) has different needs from the landscape

Each of these stages of the Black Swallowtail (Papilio polyxenes) has different landscape needs, 2014. Copyright: Ansel Oommen

Central to the success of insect conservation, however, is an equal emphasis on floral biodiversity. Simply put, each party cannot be evaluated without the other. Plants form complex structural communities, so much so, that the presence or lack thereof of certain vegetation can influence the presence of a target species, which in turn, can affect the overall health of urban spaces.

This is especially true with pollinators. In North America, native bees work hard during the spring and summer seasons visiting flowers. In fact, they pollinate two to three times more efficiently than the introduced honeybee via buzz pollination, especially with crops like tomatoes, squash, and blueberries. Their labor rewards both humans and animals with fresh fruits, vegetables and seeds. Without their efforts, other wildlife would face starvation in the colder months.

Caterpillars of many Lepidopteran species rely on specific host plants. For example, the blue lupine (Lupinus perennis) is the sole host of the federally-endangered Karner blue butterfly while the monarch depends entirely on milkweed (Asclepias spp.).

Monarch caterpillar on the common milkweed (Asclepias syriaca), one of its host plants

Monarch caterpillars on common milkweed (Asclepias syriaca), 2014. Copyright: Ansel Oommen

As a result, butterflies and moths are key biomarkers of local diversity. A decrease in their abundance and variety can signify a degenerative landscape dominated by exotic plants. Conversely, a native themed landscape is more likely to attract rarer species. In addition, caterpillars serve as a major food source for songbirds, who time their reproduction on larval emergence. Thus, insect conservation goes hand in hand with the conservation of more popular birds, mammals, reptiles, and amphibians.

Landscape architects and urban planners are in a unique position to address this issue of habitat loss through careful ecologic design and stewardship. As with business, local support is directly beneficial. Selecting native plants for urban design creates buffering green habitats in otherwise inhospitable sites. By simply being more conscious of native species, designers can add a layer of sustainability (without sacrificing aesthetics) to areas such as universities, residential plots, roadsides, green roofs, and open spaces.

Under current design practices, nonnative plants are often used, sometimes to ill effect. Unlike their native counterparts, exotic plants lack the natural pests and diseases that keep them in check and when coupled with vigorous growth and reproduction, can quickly become an issue. While most introduced plants pose little threat, some get out of control, undermining the structural integrity of the landscape and surrounding areas. In the process, they displace native communities, alter food chains, reduce aesthetic appeal, and create significant economic and environmental costs.

The autumn olive (Elaeagnus umbellata), Tartarian honeysuckle (Lonicera tatarica), and multiflora rose (Rosa multiflora) were all once planted in the U.S. with good intentions. They are now listed as noxious weeds in several states. Providing seasonal interest in the form of flowers and fruits, these shrubs were originally used for erosion control, cover, and food for wildlife. In hindsight, native alternatives such as Maple-leaf viburnum (Viburnum acerifolium), coral honeysuckle (Lonicera sempervirens), and climbing prairie rose (Rosa setigera) would have been more suitable.

Indeed, it is important to note that weeds can be native or non-native, invasive or non-invasive, or noxious, if designated by a form of government as harmful to the landscape.

However, in certain cases, weeds can be beneficial. Dandelions and clovers add an element of life to the green desert that is the manicured lawn, and yet, the internet is full of articles on how to kill them.

At the root of this injustice is a lack of awareness. Our perceptions of what we deem as acceptable built environments can be based on misguided values, which then inform our actions. But it is important to think about the grand scheme of things in the long term beyond us. Dandelions are a magnet for bees, flies, beetles, and butterflies. Widespread and hardy, they are reliable bloomers during the early parts of spring, when other nectar sources are scarce and when pollinators are most vulnerable. Clovers were originally added to lawn mixes to fortify grasses through nitrogen fixation and for evergreen, drought tolerant cover. By razing them or using herbicides, an entire microhabitat is destroyed, endangering the future of the local denizens. Multiply this by the neighborhood and city levels and the effects become more apparent.

Somewhere along the way, public acceptance has grown for sterile landscapes. But thankfully, it is equally possible to shift that demand for green spaces to landscapes that sustain life— to those areas that brim with the hum of bees, the chitter of songbirds and the cooling splashes of verdure alongside networks of houses, cars, and people– a place that is equally for them as it is for us.

As a result, designers must also be educators, informing clients about the benefits of investing in a sustainable future. There is pride to be had, beauty to be felt, and a true sense of accomplishment to be shared in being part of a mindful landscape. Change is slow but time is not. We have a direct stake in this matter. The time to act is now.



Ansel Oommen


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