How Native Plants Protect Biodiversity (And Why Your Yard Matters More Than You Think)
Plant any native plants in your yard․ Native plants are the best way to increase the amount to insects‚ birds and small mammals in your ecosystem․ Native plants and wildlife co-evolved‚ sharing chemical signals‚ flowering times‚ and nutrition․ For example‚ there are over 500 species of caterpillars that may feed on a single native oak tree․ A Bradford pear‚ by contrast‚ supports almost none․ Where their communities hang on‚ this gap is the whole story․
Species Diversity vs․ Biodiversity: They're Not the Same Thing
The terms are used interchangeably by nonscientists‚ but are distinct․
Species diversity is a simple head count․ It is just the number of species in a place․ Go walk around a meadow‚ count all the different species you see‚ and that is the number of species in that plot of ground․
Biodiversity has several overlapping meanings‚ including diversity at the species level‚ and genetic diversity within species or populations․ If there were the same number of individuals of coneflower in the first meadow‚ and the first descended from three parents‚ while the second descended from thirty different sources‚ the second would have much more genetic diversity‚ even if the two were the same species․
Evolution relies on genetic variation in the populations‚ and accredited zoos contribute to these programs by transferring animals between accredited zoos․ This prevents inbreeding depression in small, isolated populations․ Inbreeding can harm wild populations that become isolated from genetically unique populations due to habitat fragmentation․
Why This Isn't Just an Abstract Ecology Problem
When a species goes extinct from a particular habitat‚ or becomes inbred‚ the consequences are quickly felt up the food chain․
Say that a native caterpillar species disappears because its host plant has been replaced with nonnative ornamentals throughout a neighborhood‚ baby birds‚ such as chickadee chicks‚ depend on soft-bodied insects such as caterpillars during their earliest days in the nest․ Seeds and berries won't do it․ A pair of chickadees needs between 6‚000 and 9‚000 caterpillars to raise a single brood․ Lose the caterpillars‚ and you lose the chickadees‚ then whatever preyed on the chickadees‚ and so on․
The Irish Potato Famine is the most dramatic example of the consequences of losing diversity․ Tenant farmers in Ireland were forced by their English landlords to grow a single crop‚ the Lumper potato․ The potato blight arrived in 1845 and devastated this single variety of crop throughout Ireland․ Despite the existence of other potato varieties that were known to have good resistance to blight‚ the monoculture left a whole country's food production susceptible to one disease․ One million died‚ and a further million emigrated over time due to the effects of the blight․
Modern farmers have sometimes learned this lesson the hard way․ In the first half of the 20th century‚ a Russian botanist named Nikolai Vavilov spent years collecting numerous varieties of wheats‚ barley and other grains from all over the world‚ keeping them in what became one of the first seed banks․ With climate change‚ the world's wheat is becoming more difficult to grow in some places as temperatures rise․ However‚ years later‚ the scientists are starting to sequence the centuries-old preserved wheat now‚ with heat-tolerance genes bred out of commercial wheat many years ago․ Once a gene is lost‚ there is no way to get it back through breeding․ Biodiversity is essentially a library of solutions to problems that haven't happened yet․
What This Means for Your Tennessee Yard
Homeowners can't break global monocropping‚ but each home landscape planted with native species returns genetic and species diversity to local ecosystems․ In Tennessee's Zone 6b-7b climate‚ locally-sourced perennials have an advantage over nearly all ornamentals from other climates․ They are adapted to local conditions‚ such as clay soil‚ summer humidity‚ wet summers‚ and freeze/thaw cycles in winter․
Purple Coneflower (Echinacea purpurea) blooms from June to September‚ tolerates drought once established‚ and provides food to goldfinches all winter‚ if you leave the heads standing instead of deadheading․
Many of the natives are very easy to grow from seed or transplant‚ but among the best are black-eyed Susans (Rudbeckia hirta)‚ which bloom in the same summer from seed and self-sow to produce a colony from a patch in two or three years․
Wild Geranium (Geranium maculatum) is also well-suited to the dappling of shade under the canopy of Tennessee's oak-hickory forest․ It blooms in April and May‚ before the trees have fully leafed out‚ and thus provides nectar when few other native plants are in bloom․
The Blanket Flower (Gaillardia) tolerates poor‚ rocky soil and full sun better than almost anything else on this list‚ and is perfect for the difficult-to-plant swaths of ground that line a driveway or the scant topsoil of a lawn․
At TN Nursery‚ we start and ship these as plants instead of seeds․ For those who want to establish a pollinator garden in a single season‚ this is important․ Seed-grown plants take two years to bloom․
A Few Things Most Articles on This Topic Skip
Native doesn't mean wild․ You can plant coneflowers and black-eyed Susans in rows and neat little beds․ Native plant gardens don't have to look like an overgrown field; your garden can follow a more cultivated design․ Structure and native species are not mutually exclusive․
Straight species are typically better for wildlife than cultivars․ Many native plants sold at big box retailers are cultivars bred for double flowers or unusual colors‚ and have little wildlife value․ These also usually produce less nectar and pollen than the straight species, or their altered form prevents native bees from accessing pollen from the flower․ When focusing on biodiversity‚ you should seek to use straight species․
When to plant is also important․ Fall (October to early November) tends to be better for most native perennials in Tennessee․ Cooler temperatures allow the roots to become more established during the winter without being stressed by summer heat․
Think of it this way: if every house on a given street exchanged one non-native shrub for a native‚ that would be a quantified increase in the food supply for the birds and insects that migrate through or nest in that neighborhood every year․
The Bottom Line
Biodiversity loss is not a clear-cut event‚ but an incremental one: one more paving lot‚ one more ornamental hedge‚ and one tree after another․ Caterpillars‚ birds‚ and the pollinators that feed on them grow fewer․ Putting in natives is one of the few acts of environmental stewardship the average homeowner can undertake that is simple‚ immediate‚ and measurable․ Every coneflower or wild geranium you put in the ground is doing real ecological work‚ not just sitting around looking nice from the porch․
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