How do I summarize a 90 minute presentation by a knowledgeable, well organized, articulate and engaging speaker like Doug Tallamy? Below is an attempt to relay the basic information in a brief and hopefully coherent manner.
All our culture depends on the existence of healthy ecosystems surviving somewhere. New York City, for example, exists only because oxygen replenishment, air pollution removal, potable water and food supplies are provided by viable ecosystems external to the city. We simply cannot survive if not enough of “out there” is functioning.
Some 80% of our food depends on pollination by means other than wind, thus various species of organisms. Most of the food web is dependent, directly or indirectly, on arthropods (insects, spiders etc.). For example, over 90% of our bird species raise their young on caterpillars and such. No supply – no young birds, no matter how much seed is supplied in birdfeeders. Insects even make up a significant portion of the diets of large mammals such as foxes and even bears. Without insects, our biodiversity, and hence the system that sustains us collapses. If you walk in the woods, you do not see widespread damage by pests, despite the lack of pesticide intervention. The greater the biodiversity, the less there is opportunity for any one organism to dominate and devastate, and as a result, most everything thrives.
Our native insect species are adapted to eat our native species of plants. Most are unable to utilize alien ornamentals due to different chemicals they produce in their foliage. Butterfly bushes, for example, provide nectar for butterflies, but are not a food source for any species’ larval form. If you have no larval food plants, you don’t get adults. A well known example is the monarch butterfly. No milkweeds = no monarchs. Oaks, for example, support more than 550 species of insects, while many alien ornamentals support just a handful, or none.
Roads and other paving cover the equivalent of five (5) times the size of New Jersey. Lawns, which are nearly as unsupportive of species as parking lots, cover the equivalent of eight (8) times the size of New Jersey. Some 54% of the lower 48 states has been converted into cities, suburbs and infrastructure. Agriculture utilizes around 41% of the land. Of the remaining 5%, over 3,400 species of alien plants have invaded 100 million acres, an area expected to double in the next 5 years. What is left is mostly fragmented. When an isolated 100 acre woodlot is reduced to 10 acres, it’s biodiversity declines approximately in proportion..
Favoring native species of trees, shrubs, ground covers and other plants in our landscaping enhances biodiversity and reduces the introduction of invasive alien species. It also reduces the isolation effect on existing adjacent natural habitats, expanding their effective size. Shifting one’s plant preference can bring observable increases in biodiversity such as birds in a year’s time. Nature quickly avails itself of the opportunity to restore balance. In summary, the choices of the average gardener can dramatically affect the viability of the wider ecosystem that sustains us.
