Biodiversity



Biodiversity

Definition of biodiversity: the variety of life in all its forms, levels and combinations

This definition is quite malleable, and depending on who is defining the term, is seen in various forms. Regardless of the definition, it is important to remember that biodiversity is more than a simple count of species.

Levels of Organization where biodiversity exists

Species diversity: the number or variety of species in the world or in a particular region.

Includes species richness: number of species

Includes evenness/relative abundance: are the numbers of individuals of different species even or skewed (ex. Are there 50 of every species, or hundreds of individuals of one and only a few of another)

Additions of new species, called speciation, increases species diversity, whereas extinction decreases species diversity. Though immigration and emigration of species can change species diversity in a local area, it does not change it globally.

Genetic diversity: the differences in DNA composition among individuals within a given species.

They may look very similar or even identical, but if their genomes are different, there is diversity between them.

As a species becomes adapted to the environment in which they live, typically genetic diversity decreases, as those that are best fit to survive with a given set of characteristics are more likely to reproduce. This allows the species to survive better in that area so long that the conditions do not change. However, limiting such genetic diversity can be harmful if the environment does change. A lack of genetic variety can also leave the population more apt to diseases and inbreeding. The low genetic diversity is currently a problem with many animals including cheetahs, bison, and elephant seals, though such impact has yet to be seen. It is also a problem with plants, especially when resisting disease.

Ecosystem diversity: The number and variety of ecosystems in a given area

Can also include community diversity (number and variety of biotic factors), habitat diversity (number and variety of habitats) and landscape diversity (variety and geographic arrangement of habitats, communities, or ecosystems, including the sizes, shapes, and interconnectedness of patches of these entities)

A seashore of rocky and sandy beaches, forested cliffs, offshore coral reefs and ocean waters has much more biodiversity than the same physical space of a monoculture cornfield.

Measuring Biodiversity

Imagine travelling all over the world, getting to the far reaches of the Earth, and counting every single individual species that exists. Do you think you’re up for the challenge? Chances are, you’d never finish. An accurate measurement of the number of individual species is nearly impossible, even in smaller areas than the entire world. Instead of scientists counting individuals, they typically rely on species diversity, specifically species richness – how many species exists, versus how many individuals exist. The true number of how many of those species exists is a number that can only be estimated, and not all that well at that.

As of 2002, 1.75 million species of plants, animals and microorganisms have been identified. It is assumed that the total number of species is somewhere between 3 and 100 million, with the best guess somewhere around 14 million.

Species are not evenly distributed amongst plants, animals and microorganisms.

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Kenyon, Sarah. Catch a Bug. Pulse – University of Arizona. 7 March 2007.

Insects have huge predominance over all other forms of life – more than 50% of all life are insects. Of the insects, more than 40% are beetles. Beetles outnumber all noninsect animal and all plants. However, this is just from the numbers that we have counted. These number may be changed is more species are found.

So why are these estimates so incomplete? A few reasons play a part.

- Some areas on Earth are not well explored. Do you think you could survive in a hydrothermal vent to collect species? What about the deepest parts of the ocean or the tree canopies of the rainforests? These areas are difficult to reach.

- Many species are so small that they are quickly overlooked. Typically these include bacteria, archaea, roundworms, fungi, protists, and soil-dwelling arthropods.

- Some species are so difficult to identify that they end up being different organisms than originally thought. These can be both very small and very large organisms.

There have been some attempts to inventory every species on Earth. One group, known as the All Species Foundation is doing just that. The hope was with somewhere between $1-$3 billion and 25 years, the goal would be accomplished. This started in 2000, and although they are not as far along as they would have hoped at this point, the efforts still continue.

How can you help?

You can measure biodiversity where you live. There are more and more organizations trying to get involved with this effort, where biodiversity is measured in “everyday” places. One example of this is the annual bioblitz, where taxonomists and other interested citizens for groups and survey every species for 24 hours. The first of these events was held in a park in Washington, D.C., where over 1,000 species were identified. As of 2003, over 75 of these events have been held worldwide.

Global biodiversity is not distributed evenly

The distribution of species is not even. Some species contain many more individuals than others. Distribution is also not even in terms of biomes. Forests typically have more species than a tundra or taiga. Typically, when looking at a map of the diversity of organisms, the closer to the equator you move, species richness increases. This is known as latitudinal gradient. This may be because of greater amounts of sunlight, heat, and humidity, allowing that area to be more productive and support greater numbers of species. In addition, certain areas have been hit more intensely with outside pressures causing populations to decrease.

Biodiversity Loss and Species Extinction

Extinction: occurs when the last member of the species dies and the species ceases to exist.

Extirpation: extinction from a given area, but the species is not entirely gone. This can often lead to extinction. The tiger is an example – it has been forced out of much of it’s natural range, but is not yet extinct

Extinction is natural

Imagine a world filled with all of the species that ever existed – dinosaurs, trilobites, ammonites, and the millions of other species that have already gone extinct. There would be no where to move, because the world would be packed with plants and animals. However, this is obviously not the case. Before humans ever had an impact on the rate of extinction, many species fell extinct. It is estimated that 99% of the species that ever existed are already extinct. Most extinctions that occurred before humans happened one by one, at a rate known as background rate of extinction. This rate indicates that one species will go extinct every 500-1000 years. However, since the arrival of humans, this rate has increased sharply.

The Earth has experienced 5 previous mass extinction episodes

In the last 440 million years, there have been 5 mass extinctions that have occurred, each taking more than 1/5 of the families, and ½ of it’s species. The most severe case of this occurred 248 million years ago, where 54% of families, 90% of all species, and 95% of all species became extinct. The most famous mass extinction occurred 65 million years ago when an apparent asteroid his the Earth, ending all of dinosaurs and many other groups.

Humans have set the sixth mass extinction in motion years ago

It is possible and probably that we are in the midst of a sixth mass extinction. It is different from the past 5 because humans are causing it, and humans will suffer from it. Shortly after humans arrived in new areas over the past 50,000 years, the numbers of species greatly declined, especially of large mammals. In some cases, those large animals no longer exist, such as the dodo bird. Although some scientists believe this sixth mass extinction is due to climate change instead of hunting, many believe that the arrival of humans and loss of species is more than just a coincidence.

Current extinction rates are higher than normal

Humans have raised the rate of extinction for the past several centuries well over 1,000 times of the background rate of extinction due to human destruction of habitat. According to the Global Biodiversity Assessment by the UN, 30,000 plant and animal species face extinction in the preceding 400 years. Some species are becoming extinct faster than ever before. In 1995, the rate of tiger extinction was 40 times faster than ever before, and in 2002 between 50 and 100 times faster. 45% of the Earth’s forests, 50% of the mangrove ecosystems, and 10% of the coral reefs have been destroyed due to human activity.

To keep track of all of the endangered species, the World Conservation Union created a Red List, an updated list of all of the species facing high risk of extinction. In 2003, the red list reported 24% of mammal species and 12% of bird species are threatened with extinction. For all other groups, the percentages vary from 39%-89% of species in serious danger. Since 1970, 58 fish species, 9 bird species, and 1 mammal species have become extinct and in the US alone in the past 500 years, 236 animals and 17 plants are confirmed to have gone extinct. As of 2003, 1,130 mammals were on the Red List and this number continues to increase regularly.

The major causes of species loss spell “HIPPO”

Habitat alteration: Almost every human activity has the potential to alter the habitat of the organisms around us. Farming replaces diverse habitats with monoculture farms of few species. Grazing changes the species composition of grasslands. Both agriculture techniques can lead to desertification. Clearing of forests removes the food, shelter and other resources for forest-dwelling species. Hydroeleectric dams turn rivers into reservoirs upstream and affect water quality downstream. Urbanization and suburban sprawl changes the ecosystems of the more populated areas, forcing species to move out of that area. Global climate change threatens to alter habitats on large scales, as seen in the arctic with the melting of the ice.

Most of the time habitat alteration poorly affects the species that live there, as they have adapted to that climate and often struggle to survive with any changes. There are some exceptions to this, such as starlings and pigeons, that do quite well in urban environments. However, these types of species are few; for every species that benefits, far many are harmed.

Habitat alteration is by far, the greatest cause of species extinction.

Invasive species: The introduction of species into an environment that they are not naturally found in has pushed native species toward extinction. Sometimes these introductions are accidental, such as marine organisms being transported between continents in ballasts of ships, animals that have escaped the pet trade, and weed seeds sticking to clothing. Other introductions have been purposeful. For example, immigrants have brought food crops and domesticated animals to new places, and people have transported certain organisms to places for aesthetics an economic reasons unaware of the environmental issues.

Most of the time, species new to an area do not survive. However, some do very well because they find themselves in an environment without predators or parasites that would normally keep the population at bay. There is also the potential of little or no competition that they had in their previous environment. Without these limiting factors, these introduced species flourish and can displace the native species. In addition to pushing native species sometimes to extinction, economic damage can be huge from these species.

One example of the huge devastation of an invasive species occurred in Hawaii. Feral pigs were introduced to the island. These pigs dug through the dirt, consumed plants, trampled vegetation, and spread seeds of invasive weeds. The hoof prints of the pigs along with the holes that they dug in the soil left holes for water to pool, leaving a favorable environment for mosquitoes to breed. Unfortunately, the increase of mosquitoes lead to an increase in malaria, as they are vectors for the disease. This disease has decimated the population of native birds. Because these birds have been isolated for so long on the island, they have little if any defenses to competition and disease. The introduction of these feral pigs has caused a huge impact to the native species.

Other common invasive species include the mosquito fish, zebra mussel, kudzu, asian long-horned beetle, cane toad, bullfrog, gypsy moth, European starling, mongoose, Caulerpa taxifolia (algae), cheatgrass, and the brown tree snake.

Pollution: Pollution can negatively affect organisms in many ways. Air pollution can degrade forest ecosystems. Water pollution can affect fish and amphibians. Agricultural runoff, including fertilizers, pesticides, and sediments, can harm many terrestrial and aquatic species. Toxic agents such as PCBs can have substantial effects on species, as can oil and chemical spills.

Population growth: Our continued population growth poses a threat to other species indirectly through a number of avenues. These include the other components of HIPPO. More people means more habitat alteration, more pollution, more overexploitation, and more invasive species. Along with the growth in resource consumption by affluent societies, human population growth is the ultimate reason behind many of the threats to biodiversity.

Overexploitation: Overharvesting of species from the wild and overconsumption of resources. This includes hunting and poaching. Species, such as tigers, have been overexploited for specific parts for traditional medicine. Elephants have been killed for the ivory tusks. Sharks are killed for their fins to make soup. Some species have been killed for their meat, but to such great numbers that they are endangered, such as gorillas. The ever increasing use of paper has caused the demise of many species as well, as the forest loss has had a significant impact on forest dwelling species.

Sometimes causes of biodiversity loss are difficult to determine

Though there are five typical reasons (HIPPO) why species are threatened, endangered, or extinct, it is not usually a single one that is the cause of such events. It is usually a combination of those, along with other potential problems that cause the demise of species. It can be difficult to pinpoint the cause of the demise of these species as the combinations make it such.

Benefits of Biodiversity

There are both tangible , concrete reasons for why biodiversity directly and indirectly supports the long-term sustainability of human populations as well as ethical and aesthetic reasons.

Biodiversity provides valuable ecosystem services free of charge

• Provides food, fuel and fiber

• Provides shelter and building materials

• Purifies air and water

• Detoxifies and decomposes wastes

• Stabilizes and moderates Earth’s climate

• Moderates floods, droughts, wind and temperature extremes

• Generates and renews soil fertility and cycles nutrients

• Pollinates plants, including many crops

• Controls pests and diseases

• Maintains genetic resources as key inputs to crop varieties, livestock breeds, and medicines

• Provides cultural and aesthetic benefits

• Provides us the means to adapt to change.

Top Predators play key roles in their ecosystems

Many food chains are dependent on all species in that chain. If one species is removed, others may no longer have the food that they need, or other species may be able to grow out of control. These species are known as keystone species, as its removal would result in significant changes in an ecosystem. One example of how such removal can be seen with the sea otter. Removal of this species allowed the number of sea urchins to rise greatly, consuming much of the kelp. These kelp forests provided habitat for many other species that were now lost. Sea otters were removed due to overhunting as well as orcas eating them because their other sources of food were decreased.

Top predators are often most at risk in ecosystems because of their size, they are often hunted as a source of meat or thought to pose a risk to humans or livestock. They also need a large area of habitat and as habitats are destroyed or infrastructure built on them, these large mammals no longer have space to find food and survive. Because large predators often produce only a few offspring (k-strategists), they are at high risk for depletion.

Biodiversity gives us natural classrooms

If it wasn’t for diverse ecosystems, we would not have the opportunity to study and learn from the species that live there. These areas provide educational and social benefits including the study of biology, natural history, ecology and chemistry, as well as places for painting and photography.

Biodiversity enhances food security

Having multiple forms of species that we eat allows the species to persist despite bouts of disease. In addition, through research we have found foods that produce products that are usable for human consumption. For example, the babassu palm produces more oil than any other plant, and the serendipity berry produces a sweetener 3000 times stronger than table sugar. There are also now some plants that are salt resistant and can be watered with ocean water – a great way to not have to use potential drinking water. The greater the biodiversity of species, the more options exists for human consumption.

Biodiversity provides traditional medicines and high-tech pharmaceutical products

Medicines have been made from naturally from the chemicals found in naturally occurring products. It is possible that future cures for diseases, such as cancer and HIV will be found in species that already exist and every lost species is a potential lost cure. Aspirin originally came from a wild plant, an anticoagulant was originally collected from leeches, and a chemical commonly used to treat cancer, stomach disorders and motion sickness known as hyosine comes from the bark of an endangered tree. An effective disinfectant can be made from a chemical from the bulldog ant, and a chemical in the crocus flower can be used to treat cancer. The possibilities are endless, so maintaining or increasing the biodiversity that exists is imperative.

Biodiversity provides economic benefits through tourism and recreation

The tropics in many developing countries have impressive biodiversity and landscapes and are sought out by people looking for vacations. Such tourism allows an economic opportunity for those that live in those areas. Visitors spend money at local businesses, hire local people as guides, and support the parks that employ local residents. This has been the case in Costa Rica with its rainforests, Australia for the Great Barrier Reef, Belize with its reefs, caves and rainforests, and Kenya and Tanzania with their savanna wildlife. The US should not be left off of this list, as they have large national parks that draw millions each year. Because of the economic benefit it brings, ecotourism serves as a powerful incentive for nations, states and local communities to preserve natural areas and reduce impacts on the landscape and on native species.

As ecotourism increases in popularity, the potential for the degredation of the wildlife and landscapes is possible. There is a significant debate to be had over the benefits for local communities and the effects to biodiversity.

The ethical responsibility to prevent species extinction

On one hand, humans are part of nature, and like any other animal we need to use resources and consume other organisms to survive. In that sense, there is nothing immoral about using those resources. On the other hand, we have the ability to make conscious decisions about our actions and can choose what actions we take. As such, we have an ethical responsibility to make appropriate decisions and preserve each individual organism. Coming to a decisions between these two opposing sides is difficult, but worth the thought of where you stand.

Conservation Biology: The Search for Solutions

Conservation Biology

Although talk and writing about conserving Earth have existed since the time of ancient Greece, efforts the way we seem them today to conserve individual species is a relatively new phenomenon in the last few decades. As extinction rates continued to climb, the discipline of conservation biology arose, which is devoted to understanding the factors, forces, and processes that influence the loss, protection, and restoration of biological diversity within an among ecosystems. This science is often looked at as a combination of typical science research in combination with activism, as all those that are involved seek not only to understand why extinction is occurring, but also attempt to reduce it in whatever way will work best.

Island Biogeography Theory is a Key Component of Conservation Biology

Much of conservation biology is based on the equilibrium theory of island biogeography. This theory was originally created with oceanic islands in mind, and how species come to be distributed around them. Since the 60’s when it was created, researchers have expanded this theory into other “island” ideas, including islands of habitats, where one habitat is isolated from others. In addition to water barriers, this can also occur because of mountains, changes in climate, etc. This theory predicts the number of species on an island based on the island’s size and its distance from the nearest mainland. The number of species results from a balance between immigration and extinction, and the balance of the two being equilibrium.

A number of patterns can be seen using this theory.

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This pattern shows that as immigration rates are higher on islands with fewer species (because each new immigrant represents a higher proportion of the total species). It also shows that extinction rates are greater for islands with many species (because of competition, limited resources).

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This pattern shows that immigration rates are higher for large islands than for small islands. This is most likely because a large island is a greater land mass for species to find. This also shows that large islands have lower rates of extinction than small islands. This is because there is greater space for large populations, and therefore it is less likely that an entire population will die out. Together, this shows that that large islands tend to host more species at equilibrium than small islands.

The last pattern looks like this; which shows the relationship between the distance between an island and the nearest continent –

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This graph is showing the distance effect; the farther an island is from a continent, or from a source of immigration, the fewer species live on that island. These remote lands are harder to reach, therefore fewer individuals find them; however, the proximity to mainlands has no effect on extinction rates.

These theories have been supported from real-life study of species on islands. They also hold up to terrestrial habitats that have been fragmented

Some species act as “umbrellas”

Some species require large habitats to survive and can be excellent tools for conservation. Because of their vast habitat, conserving their habitat will lead directly to the conservation of many species under their umbrella. For example, conserving the tiger species will help conserve the habitats of thousands of other animals, plants, fungi and bacteria that otherwise, may not have gained such attention.

Should endangered species be the focus of conservation efforts?

Using large or charismatic mammals, such as the panda, has been an effective measuring for spearheading conservation efforts. As of 1973, , the Endangered Species Act was passed in which the government forbade anyone to take action that would further threaten an endangered species or their habitats, in addition to prohibiting trade of products of endangered species. The goal is to prevent extinctions, stabilize declining populations, and when possible, allow for recovery of populations to the point that they no longer need protection. The Endangered Species Act has had many successes, including the banning of DDT which helped restore the population of many large birds. Approximately 40% of declining populations have been held stable despite underfunding to the US Fish and Wildlife Service and the National Marine Fisheries Service which are responsible for upholding the act.

Though most Americans support the efforts of the Endangered Species Act, some have been outright vocal about their opposition to this act. Most of the resentment has been from the perception that the ESA is focused only on a few single species and that it values the life of the threatened and endangered species over people. For example, if a specific species living in the rainforest will be destroyed by the cutting down of the forest, opposition states that we are worrying about a single individual over land that could feed many people. Much of the opposition has come from private land owners that are fearful that their land could not be used as they wish if an endangered species is present. This has lead to a practice called “shoot, shovel and shut up” among those landowners who want to hide the presence of this individual on their property. Though these arguments are valid at times, what is often forgotten is that pulling down a section of rainforest, for example, not only protects that one individual, but all of the others that fall under the umbrella of that individual. As for the private landowners, the ESA has been amended to allow the harm of species in some way if they agree to improve the habitat for other species.

Can captive breeding, reintroduction efforts, or cloning help save endangered species?

In an effort to bring back endangered species, impressive strides have been attempted. Zoos and botanical gardens have become centers for captive breeding, raising large numbers of individuals and reintroducing them into the wild. One example is the California Condor. In 1982, only 22 birds remained. Biologists decided to take all of the remaining individuals into captivity and breed them. A fair amount of success has been seen in the last 20 years, as 80 of the 200 birds raised in captivity have been released. Unfortunately some of these efforts have been met with controversy, such as the reintroduction of wolves into Yellowstone National Park, as ranchers are fearful that they will attack their livestock and have consequently been shot.

The newest idea for saving these endangered species is by cloning. DNA of some species is being saved so that in the future, genetic technology will be advanced enough to produce viable individuals from that DNA. Scientists have also talked about extracting DNA from preserved bones of extinct species with the hopes of bring them back to life as well. However, without ample protection of these species once they are created, these efforts will be useless.

International conservation efforts include widely signed treaties

Since the 1970s, there have been many international efforts to protect biodiversity. As of September 2003, 188 nations have joined the Convention of Biological Diversity, set up in 1992, which has three goals; to conserve biodiversity, to use biodiversity in a sustainable manner, and to ensure the fair distribution of biodiversity’s benefit. Interestingly, of all of the countries that are not part of this group, the US is one. For various reasons, the US government is no longer widely regarded as a leader in biodiversity conservation efforts.

Nongovernmental organizations also play a role

Possibly because the US government has refused to join forces with on the Convention of Biological Diversity, there are many nongovernmental organizations that have been created by citizens that have a vested interest in the field. These include organizations such as the Wildlife Conservation Society, World Wide Fun for Nature, Conservation International, World Wildlife Fun, and the Nature Conservancy. These organizations have large budgets and often spend most of the money purchasing habitat, but also provide areas of education and training.

Biodiversity hotspots pinpoint areas of high diversity

Areas that contain the most amount of biodiversity are often called hotspots. These areas often contain species that are not found anywhere else on Earth, called endemic species. In order for an area to be classified as a hotspot, the location must have at least 1500 plant species. In addition, that area must have experienced extensive habitat alteration or other human impact already and be in danger of suffering more. Lastly, 70% of the original habitat must already be lost. There is a current list of 25 hotspots which covers 1.4% of the planet’s land surface, but contains 44% of all plant species and 35% of animal species. The purpose of creating these hotspots is to create areas to be concentrated on for conservation purposes, as such efforts in small areas will be felt greatly.

Community-based conservation is a population approach today

To encourage people to become stewards of the land that they live on, community based groups have become quite popular, protecting small areas where they live with the goal that many small efforts will lead to a large effect. Though sometimes this can limit the access to certain resources, such as potential farmland, it does guarantee that resources that do exist will be available for a much longer time. Because of our ever increasing population, many conservationists believe that simply creating parks and reserves will not be enough to support the needed biodiversity, but that smaller community based projects will be crucial for the sustainability of our biodiversity.

Further investigation strategies are being employed

Because of more and more stress being placed on conservation, new strategies to maintain or increase our levels of biodiversity have continued to be researched and in some cases, employed. One such plan is called the debt-for-nature swap, where non-governmental organizations pay off a portion of a developing country’s debt in exchange for the promise of the recipient country setting aside reserves, funding environmental educational programs, and managing protected areas. Another program created by Conservation International is conservation concession. Often, nations sell the rights of particular areas of land to corporations, giving them the right to use the resources on that land as they see fit. Often, these corporations take the resources from this land and send it oversees – often to the US, or other countries that manufacture goods. Conservation International has paid countries to not do this, which allows those countries not only to receive this money, but also to keep their resources. Surinam, in South America is a good example of this. They have received $15 million so far, and have kept their pristine forests as well as increased ecotourism and sustainable agriculture.

Conclusion

The loss of biodiversity on our planet threatens to result in mass extinction throughout the world, similar to those that have occurred in the past. Human-induced habitat alteration, invasive species, pollution, population growth, and overexploitation of resources are the primary causes of biodiversity loss. This loss matters because of the many benefits, to the point that humans could not exist the way they currently do with such a loss. As a result, many conservation biologists are attempting to conduct science aimed at saving endangered species, preserving their habitats, restoring populations, and keeping natural ecosystems intact. Hopefully the results of these scientists will slow the loss of biodiversity that threatens Earth.

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