On Mother’s Day, I received a surprise gift. In the peach tree just outside our kitchen, an eastern bluebird and Baltimore oriole alighted simultaneously. It was approaching dusk, and the departing sun lit up the brilliant hues of each bird.
That fleeting illumination came the same week as a devastating report warning that humans – in their dramatic alteration of landscapes – are jeopardizing the survival of up to 1 million plant and animal species, “many within decades, more than ever before in human history,” according to the United Nations-supported Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, which prepared the 1,500-page report.
Elizabeth Kolbert, author of “The Sixth Extinction,” summarized the report’s key message this way: “The authors trace two diverging trend lines: one upward sloping, for people, and one sloping downward, for everything else… How long can the two trend lines continue to head in opposite directions?”
Informal studies already point to precipitous declines among insects, what biologist E.O. Wilson called those “little things that rule the world” due to their abundance, variety and centrality to food webs everywhere.
Entomologists know roughly how many butterflies (120 species) and bees (400 species) reside in Maine but can only guesstimate the total insect species count here. Frank Drummond, a professor of insect ecology at the University of Maine, puts the number at “20,000, plus or minus 5,000” – compared to just 58 species of wild mammals and about 1,500 species of native vascular plants.
Insects support birds, bats and other predators and aid in the decomposition process that builds soils. Pollinators – including bees, butterflies, moths, wasps, flies and beetles – are essential not only to agriculture, notes University of Delaware entomologist Douglas Tallamy, but to most plants on earth – and hence, life.
If we are to forestall ecological catastrophe, we need to start reconsidering our landscapes with other creatures in mind.
“Which animals will make it and which will not? We help make this decision every time we plant or remove something from our yards,” Tallamy writes in his book, “Bringing Nature Home.”
Too often, landowners unwittingly remove plants at the base of the local food web, not recognizing all the creatures they support. Nesting songbirds require thousands of native caterpillars to successfully raise a brood to the fledgling stage, and those caterpillars in turn show a strong preference for native plants.
Tallamy and colleagues conducted a study, published last fall, to determine how Carolina chickadees fared in suburban yards with different mixes of plants. When nonnative plants increased in residential yards, “both insect availability and chickadee population growth declined.” To sustain bird populations, a yard had to have at least 70 percent native species (measured in terms of plant biomass).
Yet the prevailing American landscape aesthetic favors close-cropped turf grass (mostly native to Europe), exotic ornamentals and isolated specimen trees.
It’s time for “a new way of thinking,” write Sue Reed and Ginny Stibolt in their book “Climate-wise Landscaping.” “Instead of saying, ‘I’ll try to use some natives, if possible, how about approaching every garden decision with the question, ‘Is there some very compelling reason not to use a native plant here?”
Reed and Stibolt echo Rachel Carson’s warning about a “Silent Spring” if people continue applying nonselective chemical pesticides that kill off the vast majority of insects present, even though “more than 90 percent of those insects are beneficial or benign.”
Drummond urges people to “lay off herbicides and let other species [like clovers and violets] colonize your lawn.” Letting go of a “putting-green mentality,” he says, can reduce exposure of insects to chemicals – a critical step, given declines in key pollinators like New England’s wild bee species.
Focusing on the needs of insects has given Annie Wadleigh, founder of the Portland Pollinator Partnership, a “holistic view of the environment,” she says. “You start to see things differently.”
Immaculate gardens she used to admire for their tulips and exotic ornamentals now look to her more like wastelands for wildlife. And she is more careful about getting plants from suppliers who don’t use chemical fertilizers or persistent pesticides like neonicotinoids – a proven threat to bees.
The Partnership works to help people appreciate more naturalized yards and parks with varied native plants that offer insects and birds menu options through the growing season. Key to that mix, Drummond notes, are trees and shrubs.
Shrubs and saplings represent a critical understory layer in “the architecture of nature,” Reed and Stibolt write, offering animals diverse niches that the tree canopy and groundcover cannot supply.
Too often, in an effort to tidy up woodlands, landowners remove shrubby layers along with the leaf litter that builds soil and can shelter a diversity of insects, including overwintering butterfly caterpillars. The nonprofit Xerxes Society for Invertebrate Conservation urges landowners to “leave the leaves” until late spring on lawns and perennial beds, and always in wooded areas.
What’s needed now is not just a modification of yard-care habits, Drummond says, but more of “a lifestyle change, really a philosophical change.”
The ecological payback could be significant. Unlike many bird species, most insect species are quite localized. That means property owners can – with more conscious landscaping practices – support healthy insect populations and the countless species that depend on them.
Will people prioritize bluebirds and Baltimore orioles over pristine lawns and vacuumed woods?
Wadleigh sees growing interest in ecological landscaping, not only because people discover “how thrilling it is to have the birds and insects participate in your environment,” but because naturalized landscapes are “less costly to maintain and more drought resistant.”
From her own experience and that of others, she has learned that “once you see things from an ecological perspective, there’s no going back.”