Notes
47.2: The Importance of Biodiversity to Human Life
47.2.1: Human Health and Biodiversity
Maintaining biodiversity ultimately helps maintain of human health; many medicines are derived from plants and, recently, animal toxins.
Learning Objective
Describe the benefits to human health of maintaining biodiversity
Key Points
- Most plants produce secondary plant compounds, which are toxins used to protect the plant from insects and other animals that eat them, but some of which also work as medication.
- Antibiotics, which are responsible for extraordinary improvements in health and lifespans in developed countries, are compounds largely derived from fungi and bacteria.
- In recent years, animal venoms and poisons have excited intense research for their medicinal potential; at least five of these drugs have been FDA approved since 2007.
Key Terms
- antibiotic
any substance that can destroy or inhibit the growth of bacteria and similar microorganisms
- vincristine
a particular drug used in chemotherapy
- atropine
an alkaloid extracted from the plant deadly nightshade (Atropa belladonna); used as a drug in medicine for its paralytic effects (in surgery to relax muscles, in dentistry to dry the mouth, etc.)
Human Health
Contemporary societies that live close to the land often have a broad knowledge of the medicinal uses of plants growing in their area. Most plants produce secondary plant compounds, which are toxins used to protect the plants from insects and other animals that eat them, but some of which also work as medicines. For centuries in Europe, older knowledge about the medicinal uses of plants was compiled in herbals: books that identified plants and their uses. Humans are not the only species to use plants for medicinal reasons: the great apes (orangutans, chimpanzees, bonobos, and gorillas) have all been observed self-medicating with plants.
Modern pharmaceutical science also recognizes the importance of these plant compounds. Examples of significant medicines derived from plant compounds include aspirin, codeine, digoxin, atropine, and vincristine . Many medicines were once derived from plant extracts, but are now synthesized. It is estimated that, at one time, 25 percent of modern drugs contained at least one plant extract. That number has probably decreased to about 10 percent as natural plant ingredients are replaced by synthetic versions. Antibiotics, which are responsible for extraordinary improvements in health and lifespans in developed countries, are compounds largely derived from fungi and bacteria.
Medicinal uses of plants
Catharanthus roseus, the Madagascar periwinkle, has various medicinal properties. Among other uses, it is a source of vincristine, a drug used in the treatment of lymphomas.
In recent years, animal venoms and poisons have excited intense research for their medicinal potential. By 2007, the FDA had approved five drugs based on animal toxins to treat diseases such as hypertension, chronic pain, and diabetes. Another five drugs are undergoing clinical trials. At least six drugs are being used in other countries. Other toxins under investigation come from mammals, snakes, lizards, various amphibians, fish, snails, octopuses, and scorpions.
Aside from representing billions of dollars in profits, these medicines improve people's lives. Pharmaceutical companies are actively looking for new compounds synthesized by living organisms that can function as medicine. It is estimated that one-third of pharmaceutical research and development is spent on natural compounds. About 35 percent of new drugs brought to market between 1981 and 2002 were from natural compounds. The opportunities for new medications will be reduced in direct proportion to the disappearance of species. It is beneficial to humans, therefore, for medicinal purposes and many others, to maintain biodiversity.
47.2.2: Agricultural Diversity
Maintaining genetic biodiversity of wild species of our crops that are related to domesticated species ensures our continued food supply.
Learning Objective
Assess the interactions of biodiversity with agricultural diversity
Key Points
- Agricultural diversity is driven by the demands of the topography, the limited movement of people, and the needs for crop rotation of varieties that do well in different fields.
- Resistance to disease is a chief benefit to maintaining crop biodiversity; lack of diversity in crop species risks an entire crop being wiped out by a disease to which it is susceptible.
- The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant that can be bred with existing varieties.
- Seed companies must continually breed new varieties to keep up with evolving pest organisms.
Key Term
- blight
any of many plant diseases causing damage to, or the death of, leaves, fruit or other parts
Agricultural Diversity
Since the beginning of human agriculture more than 10,000 years ago, human groups have been breeding and selecting crop varieties. This crop diversity matched the cultural diversity of highly-subdivided populations of humans. For example, potatoes were domesticated beginning around 7,000 years ago in the central Andes of Peru and Bolivia. The potatoes grown in that region belong to seven species, while the number of varieties is probably in the thousands. Each variety has been bred to thrive at particular elevations and soil and climate conditions. The diversity is driven by the demands of the topography, the limited movement of people, and the demands created by crop rotation for different varieties that will do well in different fields and microclimates.
Potatoes are only one example of human-generated diversity. Every plant, animal, and fungus that has been cultivated by humans has been bred from original wild ancestor species into diverse varieties arising from the demands for food value, adaptation to growing conditions, and resistance to pests. The potato demonstrates a well-known example of the risks of low crop diversity. The tragic, Irish potato famine occurred when the single variety grown in Ireland became susceptible to a potato blight, wiping out the crop. The loss of the crop led to famine, death, and mass emigration. Resistance to disease is a chief benefit to maintaining crop biodiversity; lack of diversity in contemporary crop species carries similar risks. Seed companies, which are the source of most crop varieties in developed countries, must continually breed new varieties to keep up with evolving pest organisms. These same seed companies, however, have participated in the decline of the number of varieties available as they focus on selling fewer varieties in more areas of the world.
The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant. These wild forms are often the source of new gene variants that can be bred with existing varieties to create varieties with new attributes. Loss of wild species related to a crop will mean the loss of potential in crop improvement. Maintaining the genetic diversity of wild species related to domesticated species ensures our continued food supply.
Since the 1920s, government agriculture departments have maintained seed banks of crop varieties as a way to maintain crop diversity. Sometimes, however, seed banks are lost through accidents; there is no way to replace them. In 2008, the Svalbard Global Seed Vault began storing seeds from around the world as a backup system to the regional seed banks . If a regional seed bank stores varieties in Svalbard, losses can be replaced from those stored here. The seed vault is located deep into the rock of an arctic island. Conditions within the vault are maintained at ideal temperature and humidity for seed survival, but the deep underground location of the vault in the arctic means that failure of the vault's systems will not compromise the climatic conditions inside the vault.
Svalbard Global Seed Vault
The Svalbard Global Seed Vault is a protected storage facility in the arctic for seeds of earth's diverse crops.
47.2.3: Managing Fisheries
Overfishing leads to fishery extinctions, loss of a food source, and affects many other species in ways that may be impossible to predict.
Learning Objective
Explain the impact that the collapse of marine fisheries will have on human diet and health
Key Points
- Dramatic changes in species composition can result in an ecosystem shift, where species compositions differ from those that had been present before the depletion of the original fish stock.
- In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction; if such trends continue, aquatic ecosystems could become unavailable as food sources.
- Sustainable seafood is seafood from either fished or farmed sources that can maintain or increase production in the future without affecting the ecosystem in which it lives.
Key Terms
- overfishing
fishing that reduces an aquatic population, or stock, to a level that is inadequate for the stock to replenish itself
- sustainability
configuring society so that each can meet his own needs and greatest potential, while preserving biodiversity and natural ecosystems, and planning for future generations to maintain this potential.
Managing Wild Food Resources
In addition to growing crops and raising animals for food, humans obtain food resources from wild populations, primarily fish populations. For approximately 1 billion people, aquatic resources provide the main source of animal protein. But since 1990, global fish production has declined dramatically. Despite considerable effort, few fisheries on the planet are managed for sustainability.
Overfishing
Overfishing is the harvest of an aquatic population to a level that is too low for that population to replenish itself. Resource depletion, low biological growth rates, and critically low biomass levels result from overfishing. For example, overfishing of sharks has disrupted entire marine ecosystems.
Overfishing
When a fish stock is reduced to a level that is too low to allow that stock to replenish itself, overfishing has occurred. In addition to eliminating major food sources, overfishing is a threat to aquatic biodiversity.
The ability of a fishery to recover from overfishing depends on the species' natural ability to replenish itself as well as the ecosystem's conditions. Dramatic changes in species composition can result in an ecosystem shift, where other equilibrium energy flows involve species compositions different from those that had been present before overfishing occurred. For example, once trout have been overfished, carp might take over in a way that makes it impossible for the trout to re-establish a breeding population.
Sustainable Ecosystem Management
Fishery extinctions rarely lead to complete extinction of the harvested species, but rather to a radical restructuring of the marine ecosystem in which an abundant species is so over-harvested that it becomes a minor player, ecologically. In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction. In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict. The collapse of fisheries has dramatic and long-lasting effects on local populations that work in the fishery. In addition, the loss of an inexpensive protein source to populations that cannot afford to replace it will increase the cost of living and limit societies in other ways. In general, the fish taken from fisheries have shifted to smaller species as larger species are fished to extinction. In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict. The collapse of fisheries has dramatic and long-lasting effects on local populations that work in the fishery, not only the fishermen who depend directly on the fish stocks but all of the workers who are part of the industry, such as chefs, fish mongers, truck drivers, boat mechanics, and many more. In addition, the loss of an inexpensive protein source to populations that cannot afford to replace it can increase the cost of living and limit societies in other ways. The ultimate outcomes of overfishing and the commercial extinctions of fish stocks could include the loss of aquatic systems as food sources and economic crises for societies that depend on them.
Sustainable seafood is a movement that has gained momentum as more people become aware of overfishing and environmentally-destructive fishing methods. Sustainable seafood is seafood from either fished or farmed sources that can maintain or increase production in the future without jeopardizing the ecosystems from which it was acquired. In general, slow-growing fish that reproduce late in life, such as orange roughy, are vulnerable to overfishing and are considered unsustainable seafood. Seafood species that grow quickly and breed young, such as anchovies and sardines, are much more resistant to overfishing and are therefore labeled "sustainable" and promoted as good alternatives.
Attributions
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Human Health and Biodiversity
- "OpenStax College, Biology. October 17, 2013." http://cnx.org/content/m44894/latest/?collection=col11448/latest. OpenStax CNX CC BY 3.0.
- "OpenStax College, The Importance of Biodiversity to Human Life. October 17, 2013." http://cnx.org/content/m44894/latest/Figure_47_02_01.jpg. OpenStax CNX CC BY 3.0.
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Agricultural Diversity
- "OpenStax College, Biology. October 17, 2013." http://cnx.org/content/m44894/latest/?collection=col11448/latest. OpenStax CNX CC BY 3.0.
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Managing Fisheries
- "OpenStax College, Biology. October 23, 2013." http://cnx.org/content/m44894/latest/?collection=col11448/latest. OpenStax CNX CC BY 3.0.
- "OpenStax College, Biology. October 17, 2013." http://cnx.org/content/m44894/latest/?collection=col11448/latest. OpenStax CNX CC BY 3.0.
- "Chilean purse seine." http://commons.wikimedia.org/wiki/File:Chilean_purse_seine.jpg. Wikimedia CC BY.