Five Ways to Make Your Yard More Biodiverse

Olive clubtail dragonfly resting on Mountain ash (Sorbus scopulina).

 

Every 30 seconds in the United States, a football field-sized chunk of natural area disappears due to development, according to research from the Center for American Progress. Most of the natural areas lost in the past two decades were on privately-owned land, which accounts for about 60% of all land in the country. Clearly there’s much work to be done, since only 3% of protected areas in the U.S. are on private land. Currently, only 12% of all U.S. land is protected, which is very bad news for biodiversity. 

Scientists see the goals set by the International Convention on Biological Diversity — protection of a mere 17% of land and 10% of oceans by 2020 — as completely inadequate to handle the Sixth Mass Extinction and the climate crisis. To stop the crumbling of biodiversity — defined as all the organisms on earth, well as the diversity of ecosystems in which they are found, and the genetic diversity within each species — efforts are now behind “30×30”, a global goal to protect 30% of Earth’s land and water by 2030.

President Biden issued an executive order soon after taking office that requires agency leaders to submit input and strategies for how the feds can conserve at least 30% by 2030. Reversing the cuts made by the Trump administration and targeting expansive areas will certainly have the quickest effect, but all important habitat ought to be saved or restored. If you feel hopeless or sickened by the extinction and climate crises made worse by unrestrained development, even a 30 by 30 foot space at home will help. We can’t put it off any longer.

Here are some objectives as you move forward: 

1. Focus on local native plants after removing invasives. There’s nothing terribly wrong with growing a few of your favorite plants—for example, I love certain clematis vines and irises, and I grow organic food to eat. But those plants don’t provide much, if any, benefit for wildlife, so a large portion of the remaining plants I’ve chosen are native species, most of which belong in my area and might grow together in their natural state. Besides being low maintenance (when properly sited), they are absolutely essential to creatures who developed special relationships with them over millennia.

Native species are superior to introduced plants not because they’re trendy or due to some prejudice or because I say so. Simply put, native plants depend on native wildlife and vice versa (when they are in the appropriate place—that is, areas where they evolved together). They’re adapted to local environmental conditions and their value is not based solely as a resource for humans or on appearance (although their beauty is remarkable!).

Plant diversity is strongly associated with species richness, including healthy insect-dominated food webs. As the essential structural and functional base of many of the world’s ecosystems, most insects are “specialists”—they can only survive with certain species of plants that they evolved with (as opposed to “generalist” species that can use many plants). For example, butterflies and moths need certain host plants that provide food for their young, and many native bees forage for pollen only on specific plants at specific times of year. Myriad other insects are able to use only specific native plants; if those plants aren’t around, the insects’ decline or disappearance adversely impacts ecosystems and other animal populations since specialist and generalist insects and other arthropods supply food for other wildlife. Besides habitat destruction and climate chaos, insects are challenged by additional stressors, including insecticides, herbicides, introduced species, and light pollution. To make things worse, stressors often happen simultaneously. A 2019 global review revealed that 40% of insect species could become extinct in the next few decades, with a staggering 2.5% decline in insect biomass per year, and warned of a catastrophic impact on the earth’s ecosystems. In 2020, researchers found that Earth lost more than 25 percent of land-dwelling insects in the past 30 years

Growing natives is an act of compassion for wildlife at our mercy. It helps to think of animals as individuals with emotions and personalities, not just species. Like us, they want to avoid suffering and live a decent life, and most need native plants in order to do so. Animals such as birds and frogs that eat insects directly are of course negatively affected, but other species are as well. Bobcats, for example, are obligate carnivores, but they need native plants since they typically eat animals that consume insects or plant matter. 

Buy plants propagated from source material that originated as close as possible to your site. Using such “local genotypes”  helps ensure that you get plants that are well adapted to your area and preserves the genetic diversity that helps plants (and animals) adapt to changing conditions. Ask growers and nurseries about their sources if you’re unsure.

2. Minimize lawn and be bold when it comes to sizing garden beds. The more space we allocate for native plants, the better. Lawn is an unnatural monoculture that provides almost no support for wildlife, so if it’s not needed, let it go. You can remove it with a sod cutter or spade, but to preserve precious topsoil, cut it short, then cover it with a half dozen layers of overlapping newspaper or a layer of cardboard with holes punched in to ensure drainage. Cover with leaf compost and allow it to break down over many months.

To get ideas for plant selection and how to arrange and space those plants, look to nearby natural areas that support local native plants, inquire with your local native plant society chapter, and check out my book (if you live west of the Cascades). Plant long-lived trees and shrubs for carbon sequestration and habitat, as well as privacy so that unnecessary fencing may be removed, allowing for a contribution to wildlife corridors that connect. Add associated understory plants, including ground covers that offer the best mulch

Speaking of space, growing perennials for pollinators’ sakes means providing at least several plants of the same species that are planted fairly close to each other so that pollinators can easily find them and so there’s enough of a particular flower’s nectar/pollen to go around. But spacing them evenly, in perfect clumps, isn’t necessary and often looks contrived, and lining them up like veggies in a kitchen garden is even worse, aesthetically speaking. Take a walk in a natural area and you’ll find perennials and other plants with an array of spacing—some close together, some further apart; most mingle with other species that they evolved with. Irregular drifts may occur, as if nature took a paintbrush to create rhythmic splashes. Repetition of plant groupings will result in a natural look and more habitat. Be sure to provide at least a couple of species that flower in unbroken sequence from early spring until fall.


3. Avoid pesticides and use organic methods. It’s imperative to not use pesticides (insecticides, herbicides, fungicides, etc.) and chemical fertilizers to prevent harm to beneficial creatures above and below ground at home and prevent toxins from entering waterways and killing downstream. The Environmental Protection Agency has registered more than 18,000 pesticides for use, and more than 2 billion pounds of pesticides are sold every year in the U.S. Pesticides are pervasive in aquatic and terrestrial habitat throughout the country and threaten the survival and recovery of hundreds of federally listed species. They don’t stay put and can kill non-targeted species, decrease biodiversity within soil, are linked to a decline in nitrogen fixation, mess up the complex balance between predator and prey species in food webs, require fossil fuels, and involve heinously cruel experiments on animals. And, the U.N. tells us that about 200,000 people die each year from pesticide exposure. Chemical fertilizers are also very problematic since they kill soil microbes and pollute groundwater and waterways, leading to dead zones, among other damages.

4. Minimize water runoff and maximize carbon storage. There’s much we can do with the water that enters our landscape, and it doesn’t have to take much effort. It may help to think of our yards as mini-watersheds and ask what we can do to make sure the water that leaves our properties is clean and won’t harm other species.

Rain gardens can collect water — from downspouts or hard surfaces where water accumulates — and slow the flow of water, cleaning it as it slowly soaks into the ground and recharges aquifers. Other elements like bioswales, permeable paving, coniferous trees, and even rain barrels can manage water responsibly in our landscapes, reducing runoff that overwhelms storm drains and pollutes waterways. But it’s the plants themselves (along with soil) that effectively filter water and store carbon. Fully and diversely planted gardens — that include long-lived large trees, shrubs and lower plants — are best at cleaning water, preventing runoff, and sequestering carbon; more so than lawn or beds that are mostly wood chips. 

Halictus ligatus on Erigeron speciosus.

Although keeping your soil covered (with plants or mulch) is a good thing for carbon storage, moisture retention and erosion control, always leave some areas with bare soil (fallen leaves and small amounts of light compost are okay), particularly in areas that face south or east. Here’s why:  70% of native bees (such as this “sweat bee,” Halictus ligatus, shown) nest in the ground (the rest raise their young aboveground in cavities, stems, tunnels or crevices). Using thick layers of wood chips, bark dust, or other such substances prevents them from being able to create their nests and if applied after nests are complete, entombs and kills the developing bees.

Also, if you grow veggies, keep tillage to a minimum, if at all. Tilling soil speeds up the decomposition of organic matter, causes erosion, releases carbon dioxide into the air, exposes weed seeds to light, destroys mycorrhizae hyphae, and generally makes soil less fertile. Unnecessary fertilizer will also release more carbon. 

Erosion concerns? Choose native plants with dense, fibrous root systems to control erosion on slopes. In the Pacific Northwest, depending on your location and conditions, consider Douglas-fir, big-leaf maple, vine maple, Oregon white (Garry) oak, madrone, serviceberry, salal,  kinnikinnick, red-twig dogwood, oceanspray, tall Oregon grape and Cascade Oregon grape, western mock orange, red-flowering currant, snowberry, western sword fern, inside-out flower, and many others.

Bushtit nests require moss, spider silk, and other natural substances.

5. Add natural elements and be lazy. Wild species need secure, dry places to spend the winter, pupate, or seek cover during bad weather, and places to raise their young:  (1) Leave the leaves on soil. (2) Include rotting logs and other dead wood in shady spots to supply the perfect home for certain invertebrates and fungi. (3) Introduce brush piles to provide shelter and maybe even nest sites for some birds. (4) If you’ve dug up rocks from your soil, create smooth rock piles or stone walls without mortar to provide cover for wildlife like amphibians and reptiles, as well as arthropods. Making all these elements as large as possible and placing them in quiet areas works best. (5) If you must “clean up,” don’t do it in fall or winter. Instead, wait until late spring and do as little as possible so that those taking cover won’t be disturbed and so that birds can find building materials for their nests, such as moss, lichen, twigs, spider silk, and dried leaves (see bushtit nest, pictured above). If all this sounds messy, it is, but it’s also easy and exactly that characteristic that supports the greatest garden biodiversity! 

Last but not least, give wildlife a drink. All animals — from birds and dragonflies to frogs and salamanders — need water, so include a gently sloping bird bath or more elaborate water feature like a pond, and perhaps a plate full of watery gravel to help creatures thrive. Although the latter is most important during dry weather, birds need water year round to keep their feathers clean and waterproof. Since many urban streams have been buried, wetlands drained, and drought is upon us, it’s the least we can do.

Golden-crowned kinglet and Townsend' warbler.

© 2021 Eileen M. Stark

Pacific Northwest Native Plant Profile: Oregon grape (Mahonia species)

Mahonia aquifolium (landscape)

Oregon grape plants are colorful western shrubs with year round appeal and chances are there’s a species that will fit into your Pacific Northwest landscape. Named after Bernard McMahon, an Irish-born American nurseryman, the genus Mahonia is a member of the barberry family (Berberidaceae). But you may also see Oregon grape classified as Berberis, indicative of the extensive debate among botanists on how to classify this species. Although included in the large genus Berberis (an alteration of the Medieval Latin barberis, or barberry, from Arabic barbārīs), Oregon grape is still known as Mahonia in most commercial horticulture, so either is correct (at least as far as I’m concerned!). 

Wildlife value
Like all native plants grown where they evolved, Oregon grape plants are extremely beneficial and attractive to wildlife. Flowers provide for pollinators like bees, moths, butterflies, and hummingbirds, while the fruits, which may remain on the plant into winter, are favorites among birds such as towhees, robins, and waxwings, as well as mammals. Some butterfly and moth species rely on Oregon grape plants to host their larvae, including the brown elfin butterfly. Year round cover may support arthropods, birds, reptiles, amphibians and small mammals.

Cedar waxwings feed on Cascade Oregon grape (M. nervosa). ©Eileen M Stark


Three species
You can’t go wrong with tall Oregon grape (Mahonia aquifolium) for an evergreen, erosion-controlling, woody-stemmed, slightly prickly screen, barrier or woodland border, as part of an unpruned hedgerow, or as an accent plant (pictured top). Aquifolium means “water leaf,” likely named after the lustrous, wet-looking surface of the plant’s leathery leaves that Lewis and Clark first noticed near the Columbia River. Introduced to Britain in the 1820s as an expensive ornamental, its holly-like, pinnately compound leaves begin a bronzy coppery color, then mature to a deep green, with orange, red, or purple highlights in very sunny or cold conditions. Dense clusters of showy golden-yellow, lightly fragrant flowers appear in early to late spring. Ripening in late summer, the dusty-blue, round to oblong berries are slightly reminiscent of grapes, hence the name. Although they are tart and have large seeds, they are suitable for jams and jellies (with beaucoup sweetener) and have traditional medicinal properties, as do the roots. 

Tall Oregon grape’s range includes most of western Washington and Oregon, parts of Idaho and much of California, as well as northeastern Washington and southern B.C. It can handle nearly full sun to shade, but being a woodland species often found growing in somewhat open forests, it prefers some shade (although very deep shade will result in fewer flowers and fruit). Though it does best in slightly moist, acidic, well-drained soil, it’s an undemanding plant that can handle many soil types and drought when established. However, it is intolerant of poorly drained soils and high water tables. Since it will gradually spread into a thicket via tough rhizomes, place it away from pathways and allow it to eventually spread into a wildlife protective clump. If you don’t plan for its growth or it somehow gets out of hand, roots may be occasionally pruned and stems may be cut (as seldom as possible) nearly to the base for renewal. Arching stems typically reach four to eight feet in height, sometimes on the lower end in garden situations.

Try growing it with trees and shrubs such as Douglas-fir, western hemlock, ponderosa pine, vine maple, Indian plum, oceanspray, serviceberry, salal, and smaller companions like sword fern, western columbine, fleabane, delphinium, and others.    

Cascade (or long leaved) Oregon grape (Mahonia nervosa) is another handsome plant, but this one grows only up to about three feet tall,Mahonia nervosa often lacks shiny leaves, and very slowly spreads into a lovely, evergreen, soil-stabilizing ground cover over many years. Nervosa means “having distinct veins or nerves” and refers to the leaf venation. Showy, fragrant, erect, pale to bright yellow flowering stalks, which put on their show in early to mid spring, are trailed by the familiar deep blue berries in late summer to fall. 

This species naturally occurs in moist to dry forests, at low to mid elevations mainly west of the Cascades including Vancouver Island, often with oceanspray, osoberry, vine maple, sword fern, salal, and oxalis, but it’s also an associate of the drier Oregon white oak and madrone habitats. It prefers shade to part shade in moist, acidic soil, but can handle drought in cool areas when established. It’s a nice substitute for invasive English ivy.

Low (or creeping) Oregon grape (Mahonia repens) is an evergreen ground cover that grows one to two feet tall and four to six feet wide. It has a large range in the west; in Washington and Oregon it is mainly found east of the Cascades growing in conifer forests, so it does well in dry, shady conditions but can take some sun. Its leaves (pictured below) may be glossy or dull, tend to be rounder and—though toothed—feel less prickly than tall Oregon grape. In nature, where its range sometimes overlaps with tall Oregon grape (and in garden situations where we often place plants that Mahonia repensdon’t belong together), it may hybridize with its cousin and produce plants that are a bit taller than the true species. 

 

 

 

 

 

 

Propagation 
All Oregon grape species are best grown from seed (without drying them), with at least three months of cold stratification outdoors (wet, pre-chilled seed may also be planted in spring). Seed germination is reportedly erratic and unpredictable. If you have established plants you may find their progeny beneath them or elsewhere, as seeds are dispersed by birds and mammals; anything but very small transplants may not survive. Cuttings may also be tried in late fall. 

As always, buy plants propagated from source material that originated as close as possible to your site. Using such “local genotypes” helps ensure that you get plants that are well adapted to your area and that genetic diversity—which helps plants (and animals) adapt to changing conditions—is preserved. Ask growers and nurseries about their sources if you’re unsure.

Do you have Oregon grape but aren’t sure which species you have? This page has a handy leaf comparison (see photo on lower right column).
 
 
© 2019 Eileen M. Stark

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Manage Stormwater at Home for Clean Rivers and Habitat

rainwater mitigation with trees

It’s another one of those exceptionally rainy days (with more to follow) and I don’t want to do laundry or even take a bath. Why? A few days ago the city’s sewers overflowed into the river, and I’d rather not add more water to an already overtaxed system that results in raw sewage killing and polluting the habitat of wild species downstream. It’s not just the abundance of rain that’s the problem: It’s our infrastructure.

Generally, the unaltered earth is perfectly capable of soaking up or directing the moisture that nature doles out to natural waterways or floodplains, and seasonal flooding is normal and natural. But our urban and suburban environments, with their ubiquitous, impermeable roads, walkways, roofs, and parking lots—as well as shortage of erosion-controlling plants—cause runoff that carries soil and toxic pollutants like oil, fertilizers, and pesticides during heavy rains. In older parts of cities, pipes and tunnels that take away domestic and industrial waste combine with water collected from surface runoff. Under normal (not too wet) circumstances, the sewage and runoff is diverted to sewage treatment plants. But when too much storm water or snowmelt can’t soak in, it overwhelms the system, creating combined sewage overflows (CSOs) that cause raw sewage and other pollutants to spill into rivers, lakes, or coastal waters. People may be told not to have contact with the water, but wildlife has no choice and suffers silently. Eventually, polluted sediment builds up in waterways, increasing water temperature and turbidity and lowering oxygen levels, resulting in deaths.

In Portland, where I live, the city is investing in stormwater management projects that (sort of) mimic nature, in an attempt to mitigate stormwater at its sources. There is a plethora of work going on and CSOs are reportedly decreasing in frequency, but even one is too many.

How to help keep water clean

We can help manage and reduce stormwater pollution and overflows, starting at home. Here are some tips; some will have immediate effect, while others will take some time and effort:

Protect existing conifer trees and plant new ones (preferably native species that historically grew in your area). A mature evergreen tree can intercept more than 4,000 gallons of rainwater each permeable hardscapeyear, quite a bit more than deciduous trees. They also provide habitat, beauty, shade and cooling and help stabilize soil. Don’t prune out lower limbs unless it’s absolutely necessary.

Renovate or construct new walkways, driveways, and patios with permeable paving, rather than concrete or asphalt.

Disconnect your home’s downspouts when feasible and install rain gardens or swales in landscaped areas. They help prevent flooding by allowing water that falls on your roof to slowly infiltrate into the ground, lessening the burden on sewer systems when it is most important. Simply disconnecting spouts and allowing water to run down a driveway or walkway and into the street defeats the purpose. Additional rain garden guides: here and here.

swale from disconnected downspout Use only organic fertilizers when necessary (excess can be washed into waterways), and don’t use pesticides.

Grow native plants that help control erosion. Some examples (that naturally occur in many parts of the Pacific Northwest) include vine maple (Acer circinatum), madrone (Arbutus menzeisii), Oregon white oak (Quercus garryana), oceanspray (Holodiscus discolor), serviceberry (Amelanchier alnifolia), salal (Gaultheria shallon), nootka rose (Rosa nutkana), sword fern (Polystichum  munitum), kinnikinnick (Arctostaphylos uva-ursi), and inside-out flower (Vancouveria hexandra). Choose plants that will fit your light, soil, and moisture conditions.

 Employ rain barrels to collect rainwater runoff from building roofs for irrigation during dry weather (if you can’t disconnect a downspout).

Conserve water simply by taking very short showers, never letting the faucet run unnecessarily, and fixing any leaks (just as you would during droughts!).

Collect “graywater” and use it onsite to reduce sewage discharges year round. Beware: this takes some ingenuity and planning!

 Never dispose of chemicals (like anti-freeze) by pouring it on the ground or into storm drains. Even drops of oil that seem relatively contained in your driveway can easily be swept into local waterways by rain. If you get an automotive oil leak, catch the oil in a pan and get it fixed ASAP.


© 2015 Eileen M. Stark

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