"When one tugs at a single thing in nature, he finds it attached to the rest of the world." —John Muir
Earth’s variety of life is known as biological diversity, or biodiversity. Generally speaking, the more variety of life that exists within a given area, the higher the biodiversity. Scientists study biodiversity at three basic levels: species diversity, ecosystem diversity, and genetic diversity. Each of these levels reveals the health of our planet in different ways.
Species diversity is what most people think of when they hear the term biodiversity, referring to the number and relative abundance of different species found within an area. A common way to measure species diversity is to count the total number of species living within a particular area.
Ecosystem diversity refers to the variety of ecosystem types found within a given region. For example, the San Francisco Bay Area contains woodland, grassland, wetland, river, ocean, and coastal dune ecosystems—giving it a high level of ecosystem diversity.
Genetic diversity exists where there are a variety of genetic traits within a single species or population. A species has high genetic diversity when individuals in the species have a wide range of genes, and as a result, individuals look or behave quite differently from one another. A genetically diverse species is generally more resilient and able to withstand unexpected changes, like an aggressive virus, for example.
According to National Geographic, tropical regions, areas that are warm year-round, have the highest biodiversity, whereas temperate regions, which have warm summers and cold winters, have less biodiversity. Regions with very cold or dry conditions, such as mountaintops and deserts, have even less biodiversity. The Amazon Rainforest of South America is one of the most biologically diverse regions on the planet, with at least 40,000 different plant species.
Ecosystems are deeply interconnected. The less biodiverse an ecosystem is, the more vulnerable it is to changing conditions. For instance, if each species in a food web is directly connected to just one other species, the entire ecosystem could collapse if just one species in the food web was threatened. By contrast, if each species in a food web is connected to multiple species, for example, in a diverse ecosystem where coyotes eat rabbits, prairie dogs, and mice, coyotes would most likely survive if one of the species it depends on experienced a sudden decline.
Some species are particularly critical to the survival of an ecosystem. We call these keystone species, as they have a disproportionate impact on their ecosystem compared to other species in the same ecosystem. For example, several species of salmon in the Northern Pacific Ocean are considered keystone species because salmon (and their eggs) serve as a major source of food for a variety of fish, birds, and mammals.
Biodiverse ecosystems are not only beneficial to the species that live in them; they also contribute to human health and well-being. Ecosystems provide services such as food, fuel, air and water purification, pollination, recreational opportunities, and many more things we often take for granted. If the balance of an ecosystem is disturbed, one or more of these ecosystem services could be impaired.
Diverse ecosystems provide economic benefits, too. Areas with high biodiversity tend to experience more tourism. Although tourism can bring along its own set of threats and challenges, it can also provide significant economic benefits to communities when tourists spend money locally, both on activities related to the biodiverse environment, and at local businesses such as hotels, restaurants, and shops.
Additionally, maintaining the biodiversity of a region is often an important part of sustaining native cultures and societies, as well as relationships between them. Because of this, the consequences of biodiversity loss can extend far beyond the affected geographical area. Declining fish populations for example, effect those who make their living from fishing, the communities that support the fishing trade, companies that distribute fish, and families who depend on fish as their primary source of protein. Therefore, biodiversity is a key component to building a sustainable future for all.