Biodiversity is the diversity of life on Earth in all forms and includes the relative abundance and composition of species and ecosystems worldwide. We sit at the top of this biological wonder and our actions are responsible for consequential changes in the natural biological systems we depend on for functioning and ecosystem stability. Global climate change, primarily due to industrialization, and increased human population are the focus for media attention on the decline of our natural world. But, the loss of species and, biodiversity along with the movement of invasive species outside their natural habitats, is of even greater consequence to the biosphere we humans depend on for our longevity, food, well being and life in a stable biological world on our planet.
To quote Edward O. Wilson, Professor Emeritus at Harvard University, and one of the leading biologists in the world: “Think of the Earth’s biodiversity, the planet’s variety of life, as a dilemma wrapped in a paradox… Do we stop the destruction of species for the sake of future generations, or the opposite, just go on changing the planet to our immediate needs. If the latter, planet Earth will recklessly and irreversibly enter a new era in our history,… an age of, for, and all about our one species alone, with all the rest of life rendered subsidiary.” A historic and convenient measure of biodiversity is the total number of species. In 1758, when Carl Linnaeus devised binomial nomenclature, (the use of genera and species) the taxonomic classification we still use today, he thought there were about twenty thousand species in the entire world. Today we discover and name about twenty thousand new species every year. Almost all of these more recent, newly discovered species, are invertebrates, fungi, and other microorganisms. Yet these seemingly inconsequential discoveries, comprise a complex system of interactions with the world we live in, where the extinction of any species, under certain conditions, can have a profound impact on the whole. The small stuff sustains the big stuff.
The current dilemma is, how can we care for the important species comprising Earth’s living environment, if we don’t know them. Biologists believe that a large number of species are being driven to extinction, before they are discovered. These species may be essential to the life and well-being of other species we recognize as an important basis for our survival. For example, we are completely dependent on tiny microbes to live – there are more than 10,000 species in our intestine digesting our food.
Generally in this age, we are not talking about the survival of large mammals. The public is more concerned about the survival of the big creatures we relate to as living beings like elephants, rhinos, sea turtles, mountain gorillas and polar bears.
But it is the loss of the small stuff that puts us most at risk.
How many species are threatened? The IUCN Red List which provides conservation status, and distribution information on
taxa worldwide that are facing a high risk of global extinction, now includes 41,415 species, and 16,306 of them are threatened
with extinction. This is up from 16,118 last year. The list includes both plants and animals.
Popular media is focused on a handful of large species, but the vast number of less noteworthy species, comprise and drive
all our biological systems on which we depend. The study of only a small number of species has given us major advances in
the quality of human life from pharmaceuticals, new biotechnology, and advances in agriculture. Yes, even in ornamental plants
that support our nursery industry. If there were no fungi of the right kind, there would be no antibiotics and no bacteria of the
right kind, no nitrogen fixation in the soil. Without wild grains, fruits, seeds, and grasses for selective breeding there would be
no agriculture. Without agriculture there would be no cities, and no civilization. Without the bounty of nature and agriculture,
there would be few if any people.
Where does wholesale nursery production fit into the importance of biodiversity? In urban landscapes homogeneous plantings
of a few cultivars, even with superior attributes are susceptible to increased pests and disease. Low urban plant diversity
sets the stage for devastation with the onslaught of new pests (remember they are evolving too) or other environmental
challenges. In the city of Seattle, 38% of all maples are Acer rubrum. Overplanting occurs not just at the species level, but
at the cultivar level as well. In Iowa, 60% of all red maples sold are of one cultivar.
The country is awash in these examples, and the urban taxpayers will foot the bill as pest and disease move in. Pests and disease,
such as Dutch Elm Disease, Emerald Ash Borer, Asian Longhorn Beetle, Japanese Beetle and Sudden Oak Death wreak havoc on
urban landscapes lacking species diversity.
Confusion on landscape practices, is common. Maximizing plant diversity, is not the same as maximizing genetic diversity
with plants selected for their suitability in the climate and conditions under consideration. Each and every species selected
to place in the landscape should be understood in relation to the whole. As human populations increase and an ever greater
part of our landscape is artificially vegetated, this becomes a critical consideration in maintaining the biodiversity and heath
of the planet.
A recent survey on the knowledge of plant species diversity by wholesale nurseries published in Arbor-culture and Urban
Forestry indicated a general awareness of the issue, but they lacked an understanding of why the lack of species diversity
among landscape plants is a problem.