What Is Biodiversity?
Biodiversity refers to the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur. Scientists have identified about 1.9 million species alive today. Scientists are still discovering new species. Thus, they do not know for sure how many species really exist today. Most estimates range from 5 to 30 million species.
Literally, biodiversity is the many different kinds ( diversity ) of life ( bio- ). Biologists, however, always alert to levels of organization, have identified three measures of life’s variation.
Genetic diversity recognizes variation within a species: differences among individuals or populations of organisms that belong to the same species. An example is diversity in hair color among humans.
Species diversity refers to the variety of different species that live in a particular ecosystem or on the Earth as a whole. An example would be the fact that the Amazon rainforest is home to thousands of different species of trees.
Finally, Habitat diversity describes the many types of functional units formed by living communities interacting with their environments.
Although all three levels of diversity are important, the term biodiversity usually refers to species diversity. For example California has many diverse ecosystems belonging to many biomes including sandy beaches, estuaries, deserts, wetlands, grasslands, and alpine forests.
Direct Economic Benefits of Biodiversity
Biodiversity refers to the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur. Scientists have identified about 1.9 million species alive today. Scientists are still discovering new species. Thus, they do not know for sure how many species really exist today. Most estimates range from 5 to 30 million species.
Literally, biodiversity is the many different kinds ( diversity ) of life ( bio- ). Biologists, however, always alert to levels of organization, have identified three measures of life’s variation.
Genetic diversity recognizes variation within a species: differences among individuals or populations of organisms that belong to the same species. An example is diversity in hair color among humans.
Species diversity refers to the variety of different species that live in a particular ecosystem or on the Earth as a whole. An example would be the fact that the Amazon rainforest is home to thousands of different species of trees.
Finally, Habitat diversity describes the many types of functional units formed by living communities interacting with their environments.
Although all three levels of diversity are important, the term biodiversity usually refers to species diversity. For example California has many diverse ecosystems belonging to many biomes including sandy beaches, estuaries, deserts, wetlands, grasslands, and alpine forests.
Direct Economic Benefits of Biodiversity
- Clothing, Shelter, and Other Products : As many as 40,000 species of plants, animals, and fungi provide us with many varied types of clothing, shelter and other products. These include timber, skins and furs, fibers, fragrances, papers, silks, dyes, poisons , adhesives, rubber, resins, rubber, and more.
- Food Supply : Monocultures (large-scale cultivation of single varieties of single species) are extremely vulnerable to disease. A water mold caused the infamous Irish potato famine where potatoes had been bred from a single Incan variety. There are actually over 8,000 different types of potatoes which could be grown. According to the Food and Agricultural Organization of the United Nations, humans currently cultivate only 150 plant species, and just four provide over half of the food we eat. Just 15 animal species make up over 90% of our livestock.
- A return to traditional farming techniques is beginning to replace monocultures with farms that grow diverse crops. Farmers are discovering that by growing a wide variety of species they have less problems with pests without the need of pesticides or herbicides, the soil remains much healthier without the need of fertilizers, crop yields are larger, and the farms are more economically stable and able to survive when one particular crop fails.
Wild varieties of domesticated crops, such as this unusually shaped Latin American maize, hold the potential to enhance productivity, nutritional value, adaptation to local climates, and resistance to local diseases through hybridization. Loss of biodiversity limits our ability to increase the genetic diversity of crops.
- Energy : In addition to these raw materials for industry, we use animals for energy and transportation, and biomass for heat and other fuels. Moreover, hydroelectric power depends on ecosystem structure: Chinese scientists calculated that the economic benefits of maintaining forest vegetation in the Yangtze River watershed “produced” more than twice the economic value of timber (had it been harvested) in annual power output.
- Medicine and Medical Models : Since the first microorganisms competed for food, evolution has been producing chemicals for “warfare” and “defense” in bacteria, fungi, plants, and animals. According to the American Museum of natural History Center for biodiveristy Conservation (AMNH-CBC), 57% of the most important prescription drugs come from nature, yet only a fraction of species with medicinal potential have been studies.
- Unique features of certain species have opened windows into how life works. For example, the Atlantic squid’s giant axon revealed the basics of neurophysiology, and the horseshoe crab’s optic nerve photoreceptors taught us how vision works. Other animals serve as disease models; as far as we know, other than humans, only armadillos suffer from leprosy, and only sea squirts from kidney stones.
Island Biogeography
Island BioGeography Theory
Why do some islands have more species (biodiversity) than other islands? When islands are larger, they typically have more species. For example, the island of New Guinea has more bird species than Bali and is 50x larger in area.
However, the Society Islands (Tahiti, Moorea, Bora Bora) in the South Pacific have fewer species than similar sized islands in the Lousiade Archipelago in the same area of the world. In addition, the Hawaiian Islands are 10x times the size of the Lousiades, but have fewer species of birds. What can explain this?
In the 1970s, ecologists E.O.Wilson of Harvard and Robert MacArthur of Princeton developed the theory of "island biogeography" to explain such uneven distributions. They came up with these generalities:
In addition, habitat fragmentation can cause edge effect. The edges of a piece of habitat have less species. This is because species that thrive in the interior of a habitat can fail to find food or reproduce near the edge. In addition, some animals may face more predators near the edges of a habitat. For example, if a habitat is fragmented due to human development, human pets can kill wild species on the edge of the habitat. Another example is when predators that favor open habitats (such as a hawk) now easily find prey on the edges of a forest. Clear-cut logging (all the trees are removed on a piece of land) can create many open patches within a forest and increase edge-effects.
Conservationists put the most importance on places with the highest biodiversity. The most important places are called biodiversity “hot spots”. Southern California is a biodiversity hot spot, because it has many different types of ecosystems—mountain, chaparral, oak woodland, intertidal zone and ocean. This allows for many different species that are adapted to these different ecosystems.
References: Ehrlich, Paul. “Island Biogeography.” Stanford University, www.stanford.edu/group/stanfordbirds/text/essays/Island_Biogeography.html. Withgott, Jay, and Matthew LaPosata. Environment: The Science Behind the Stories. 5th ed., Pearson, 2014.
K. Schertz 12/2018
Why do some islands have more species (biodiversity) than other islands? When islands are larger, they typically have more species. For example, the island of New Guinea has more bird species than Bali and is 50x larger in area.
However, the Society Islands (Tahiti, Moorea, Bora Bora) in the South Pacific have fewer species than similar sized islands in the Lousiade Archipelago in the same area of the world. In addition, the Hawaiian Islands are 10x times the size of the Lousiades, but have fewer species of birds. What can explain this?
In the 1970s, ecologists E.O.Wilson of Harvard and Robert MacArthur of Princeton developed the theory of "island biogeography" to explain such uneven distributions. They came up with these generalities:
- Larger islands have more biodiversity.
- Islands closer to the mainland have more biodiversity.
- Larger islands are bigger targets so migrating species can find them more easily.
- Closer islands are also easier to find for migrating species.
- Larger islands have higher populations of species and therefore lower extinction rates, because there is less of a chance for population numbers to drop to zero with an ecosystem disturbance.
In addition, habitat fragmentation can cause edge effect. The edges of a piece of habitat have less species. This is because species that thrive in the interior of a habitat can fail to find food or reproduce near the edge. In addition, some animals may face more predators near the edges of a habitat. For example, if a habitat is fragmented due to human development, human pets can kill wild species on the edge of the habitat. Another example is when predators that favor open habitats (such as a hawk) now easily find prey on the edges of a forest. Clear-cut logging (all the trees are removed on a piece of land) can create many open patches within a forest and increase edge-effects.
Conservationists put the most importance on places with the highest biodiversity. The most important places are called biodiversity “hot spots”. Southern California is a biodiversity hot spot, because it has many different types of ecosystems—mountain, chaparral, oak woodland, intertidal zone and ocean. This allows for many different species that are adapted to these different ecosystems.
References: Ehrlich, Paul. “Island Biogeography.” Stanford University, www.stanford.edu/group/stanfordbirds/text/essays/Island_Biogeography.html. Withgott, Jay, and Matthew LaPosata. Environment: The Science Behind the Stories. 5th ed., Pearson, 2014.
K. Schertz 12/2018