Native Plants and Biodiversity
There is a relatively thin layer on Earth, about 12 miles thick, where all living things create a quilt of habitats for life. Within these countless habitats, billions of life-forms engage ceaselessly in trillions of interactions daily to create the sustainable balance that centers on the ‘native’ plants that thrive within them. Our world has evolved so that we humans are the mind and stewards of these habitats, so it’s beneficial to better understand this role of native plants in this larger picture.
“‘Native’ is not a label a species earns after a given period of time. It is a term that describes a function.” – Douglas Tallamy
Homo sapiens co-evolved alongside the plants and animals over the past 3.8 billion years, making up the wondrous yet mysteriously complex biosphere that quite literally supports all life on earth, including us. Our human heritage is in fact a recent addition to the mix, joining the team about 160,000 years ago as hunter-gatherers, and life (for humans at least) just got better and better.
Unlike all the other creatures on Earth, these nomadic hunter-gatherer tribes began taking control of ‘nature’ with fixed location agriculture-based communities. Growing crops, burning prairies, domesticating animals, building roads, etc. Each of these ‘constructs’ sent a ripple through the ‘system’ in the ecosystem. Today the U.S. is predominantly ‘civilized’ with over 70% of us living and working in urban/suburban communities where nature has been pushed back for centuries, and development continues today at an alarming pace.
The magic of nature is in the ‘systems’ in each habitat, and the billions of interactions between life that occur there. One of the more important ‘systems’ is the process of sexual reproduction in native plants by symbiotic relationship with birds, bees, butterflies and other creatures that pollinate while searching for food. These ‘interactions’ are happening around us every day, but fewer and fewer because the loss of natural habitat is exacerbated still further by the loss of ‘native’ plants; kind of a 1-2 punch to nature.
So Why Do Natives Matter?
In their latest State of the World’s Plants, the Kew Royal Botanic Gardens report that at least one-fifth of global plant species are at risk of extinction due to a perfect storm of habitat loss, disease, pollution, and invasive species-all exacerbated by climate change and severe weather events. All land-based life–plant, animal, and insects (collectively bugs (arthropods) ants, bees, beetles, butterflies and moths (Lepidoptera) etc.–are ‘native’ to a range of conditions of particular habitat(s), and in their genetically unique ecological niches those species work in an intricate weave of interactions to maintain the balance of life there.
Here are some of the primary drivers that are impacting biodiversity in our world today:
- Loss of Habitat: An ecosystem is defined by both biotic (living, such as plants, animals and other life) and abiotic (non living such as rocks, climate, and moisture) creating a ‘habitat’ where multiple co-evolved species interact directly or indirectly to stabilize the ecosystem services. When a habitat is altered by human or natural forces, we upset the balance of life there.
- Consider that the U.S. has over 3.7 million square miles (sm), of which 54% has already been converted to urban/suburban development where over 50% of our population now lives. Of the remaining lands, another 44% has been developed into predominantly mono-culture (non-native) agriculture. In the past 250 years, we’ve lost over 70% of our eastern forests alone.
- When habitat changes are gradual, the species within will either evolve or become extinct over time. The stark reality we are faced with today is that the entirety of the world has been altered to some degree, either directly or indirectly, by human influence. We’ve bent nature to serve our need for housing, work or recreation and in doing so, have altered these habitats thereby impacting the ecosystem and upsetting the balance of life. And it’s happened so fast that the species simply haven’t had time to adapt through evolution.
- Fragmentation: Insects and animals migrate and they require a geographic area in which to thrive to provide for an ample food web and to share their genetic material by way of reproduction. For some, this can be measured in square meters; others, thousands of miles. Some fly, some crawl.
- The breaking up of a habitat isolates populations making them vulnerable to local extinction. The loss of biodiversity in one ‘patch’ of conserved land can be partially overcome if species are able to move and share their genetic material. Linking the remaining patch-work by way of a ‘wildlife corridor’ can help some species. For this reason, bio-corridors are becoming an important aspect of the conservation efforts. More on that below.
- Climate Change: This loss of overall biodiversity, based on the number of unique ecological niches, is our largest threat to a livable world for the very reason that it provides redundancies or safeguards for the health and evolution of our planet.
- Dramatic changes in weather patterns, such as increased heat waves, droughts, increasingly intense storms, floods and sea level rise are already exceeding plants’ and animals’ tolerance thresholds, again, making them vulnerable to extinction. Consequently, biodiversity acts as a climate change buffer by helping as many species as possible adapt, even if their numbers are relatively low.
- Invasives: The innocent or well-intentioned ‘introduction’ of species of plants or wildlife from one habitat to another, too often becomes a troublesome ‘invasive’ due to a change of climate.
- While a species might be harmless in its ‘native’ environment due to the balance there, it can become very aggressive when introduced to a new climate, over-competing with natives that have no defenses against it.
- Invasive plants contribute to even greater biodiversity loss and complete ecosystem alterations that might take countless generations to rebalance.
- Communication: Over 99% of all living species rely on chemical senses to find their way through the environment, and a majority use special chemicals called pheromones to communicate with each other. We humans do not share these senses, and so we don’t really ‘see’ the environment the way the rest of life does. Where we might see the introduction of a new species, say an exotic plant, into our environment as pleasing or beneficial, the rest of life will simply sense that as something to be navigated around and having no benefit. There are exceptions of course. Some wildlife will respond to non-native species, but most will not.
- Food Web: Native plants are best able to support the complex food webs necessary to sustain ecosystem functions for native and migrating wildlife because they share an evolutionary history with them. Birds, for instance, are believed to feed on native plants over 85% of the time. Non-native plants reduce the ‘carrying capacity’ of the ecosystem, meaning the ability to sustain the wildlife population there. If the wildlife disappears, so will the plants. According to Douglas Tallamy, “If pollinators disappear, 87-90% of the plants on earth would disappear.”
- Keystone Plants: Many species of wildlife require a specific native plant as the ‘host’ for their reproductive process. There are over 2,000 native plants in the U.S. and most of them serve as hosts for one or more species of caterpillars. Nearly 30% of native bees are such specialists, as well as most butterflies. Residential yards dominated by non-native plants have been shown to have 75% fewer caterpillars.
- Beneficial Insects: There are an estimated 3-4 million known insect species in the world, and over 99% of these are considered to be ‘beneficial’ in that they have a role to play in the balance of life in their respective ecosystems. Over 95% of North America’s terrestrial bird species rear their young on insects rather than seeds and berries. Our native Carolina chickadees, for example, carry 400-600 caterpillars a day to their nestlings. Migrating birds require tremendous energy, consuming enough insects in a day to increase their body weight 30-50%. However, recent studies indicate insect numbers have decreased by as much as 45%. Without insects we’d have no flowering plants, which would dismantle the food web that supports vital animals (i.e. birds), further reducing seed distribution.
- Eco ‘Systems’: Native plants participate in many ‘systems’ within their habitats, not the least of which is providing oxygen. They also filter our groundwater, control runoff, capture carbon and add it to the soil to enrich it. That builds topsoil and prevents flooding. The soil itself is part of the habitat supporting an incredible world of insect decomposers, without whom the soil would simply rot.
What Can I do? Preserve, Protect, Restore
There are limitless excellent conservation efforts to preserve natural habitat all around us here in South Carolina, and beyond; all worthy of our financial and physical support. But as E.O. Wilson points out in his final book Half Earth, and Douglas Tallamy reinforces in his book Nature’s Best Hope, although these global efforts are vital and essential, they won’t be enough.
Many of us believe it’s clear that a healthy biosphere is good for the economy. We might also trust that the public as well as our business and political leaders will recognize that the living world is an independent moral imperative, vital for human welfare. But we humans have a propensity to favor short-term decisions over long-range planning, and with the endemic social polarization of the day, the fabric of our social structure just doesn’t seem up to the task. At least, not with the proper degree of urgency needed to reduce the acceleration of native plant and animal extinctions being reported today.
The conservation/restoration effort for each habitat requires knowledge and love of the local environment shared by partnerships of the public, scientists, activists, educators, political and economic leaders. To succeed, it needs every bit of their entrepreneurship, courage and persistence we can produce. No easy task, and even so, while also vital and essential, this won’t be enough either.
What is needed is already well underway, but needs escalating. Douglas Tallamy has the right idea in his books ‘Bringing Nature Home’ and ‘Nature’s Last Hope’. With so much of the world, and right here in South Carolina, already developed, we need to encourage the restoration of individual properties by re-wilding them. We need a grassroots movement to make the preservation, protection and restoration of habitats a priority at our own properties: residential, commercial, and institutional.
Just as turf grass lawns and ‘meatball’ shrubs became the culture here in the U.S. back in the 1950’s, let’s work together to develop a new culture that strives to restore our individual property spaces back to 70% native species. This will, in turn, impact our environment and biodiversity in so many beneficial ways. To achieve this, we’ll need to reduce our turf grass lawns, eradicate invasive species, and learn to landscape with native trees, shrubs and perennials.
The South Carolina Native Plant Society is striving to educate our communities on the wonderful array of plants that belong in our South Carolina ecozones and in our climate, as our unique contribution to the challenges discussed above. We also work hard to make these plants available to the public. We share this passion with many wonderful organizations right here in South Carolina, and as more of our neighbors begin the process of re-wilding their properties, a groundswell of interest will begin to make our government and business leaders more actively involved.