1 Biodiversity
Ecosystems that were discussed in Module 3 are where we find what is termed Biodiversity. Biodiversity is defined as, “the variety of the earth’s species, or varying life-forms, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life.” Module 4 will deal mainly with living organisms and how they survive or not survive depending on many factors, including:
Their food and water sources
Places to have their offspring
External factors such as Climate
Interactions between and among species in natural populations, to name a few
There is more than one type of diversity that make up the components of Biodiversity. These are:
Functional Diversity: energy flow and matter recycling
Ecological Diversity: variety of terrestrial and aquatic ecosystems.
Genetic Diversity: variety of genetic material in a species
Species Diversity: number and abundance of species present
Review Figure 4.2 on page 79 of your textbook for the major components of the earth’s biodiversity.
2 Species Richness
Species diversity also includes the variety of species, or in other terms, the richness that we find in an ecosystem. Your textbook indicates that, “species richness appears to increase productivity, stability or sustainability of an ecosystem. (Miller & Spoolman, 2015, p. 91)”
There are two hypotheses that have come out of this speculative statement, generating two questions:
Is the plant productivity higher?
Does species richness enhance stability or sustainability?
Answers to these important questions will eventually lead to an eventual determination of the health of the world’s ecosystems.
References
Miller, G. T. & Spoolman, S. E. (2015) . Living in the Environment (18th edition,). Stamford, CT: Cengage Learning
3 Extinction
Someone once said that extinction of a species is forever. This is predominantly true, although if you consider the last few thousand years that life on earth has changed, then it is conceivable that new species will be generated to fill the void in the future. Who knows what will be found in the natural world in another 100,000 years. Somehow it is no consolation to animals such as the Northern white rhino that has only 5 members of its species alive and only one is a male. The sight of this animal grazing in a field with 4 armed guards surrounding it for protection is a sad sight and a sad statement on the human condition that has led to its near or pending extinction. Go to an article With 1 male left worldwide, northern white rhinos under guard 24 hours if you want to read more about it.
As disturbing as this situation is, it is only the tip of the proverbial extinction iceberg as hundreds, if not thousands, of other species that do not make front-page news are near extinction. Why do you think that the large species like the Bengal tiger, the Giant Panda bear and the Northern white rhino get most of the attention while other lesser species go without much human attention? Can you even name an insect or bird that is endangered without some research? If not, then here are some Internet sites to start your own research:
Saving the world’s most extraordinary species
Tell Global Leaders to Cooperate on Fresh Water
Find Endangered Species
4 Natural Selection
An important scientific theory that generally explains how life has changed over the past 3-5 billion years is called biological evolution through natural selection. As you probably are aware, this theory has generated significant opposition within human cultures and religious beliefs. The importance of this theory in this discussion is the “attempt” to explain biodiversity that we observe in ecosystems today. These long-term changes to species are in contrast to the circumstances where environmental conditions change dramatically or rapidly. In these cases, a population of a given species has 3 options: adapt, migrate, or die.
The second and third terms above are straightforward and need no explanation. Adaptation requires us to know more about whether a species will survive extinction given the new environmental conditions. These are numerous, but include coping with climate change, obtaining food and water, escaping predators and finding mates to name a few. The outcome of this is the modification of a species’ gene pool in the biotic community and ecosystem toward the features that enhance survival. Obviously, this normally is expected to occur over a long period of time and species develop traits that we observe today, such as the ability to run fast, fly, grow thorns or develop obnoxious tastes or smells. These factors also help to define what roles each species plays in the ecosystem they live and the biodiversity that exists.
5 Niche and Indicator Species
The major roles that species play within ecosystems revolve around the term niche. Niche refers to the total way of life of a species that includes their survival, reproduction and feeding. Niches are classified in terms of specific roles, so that if a species is native to the ecosystem, then it normally lives and thrives in the niche. The opposite of native is non-native or an invasive, alien or exotic species. These species can be either destructive or beneficial to the native species in the ecosystem. Indicator species provide early warnings of change to a community or ecosystem. A good example of this is the observed decline in amphibian species in the tropical rainforest. Amphibian species are very important in the ecosystems that they live as they eat a tremendous amount of insects and are food for many other species like birds, reptiles, fish and mammals. There are also untold pharmaceutical products that have yet to be discovered from amphibians.
6 Keystone Species
There are keystone species that might have the most important role in ecosystems. Their roles have a large impact on the types and abundance of other species in the ecosystem. The American alligator is an example of a keystone species. The alligator feeds on many of the other species in the ecosystem and can help to control their populations. Early in the 20th century, the alligator almost became extinct through hunting. Humans were degrading the biodiversity of the subtropical wetland ecosystems by almost pushing this keystone species to extinction and did not even realize it. If you can, think of what other species would have been adversely affected or even may have disappeared if the American alligator had gone extinct. Fortunately, the American alligator survived and is touted as a real conservation success story.
When a keystone species in an ecosystem is removed, then it tends to have a damaging impact on the biodiversity. Consider the example of a marine ecosystem where a starfish species feeds on mussels and keeps their population under control. If the starfish is eradicated, for whatever reason, then the mussel species population growth rate could increase resulting in the rocks being covered by them. This greatly reduces the biodiversity of the ecosystem by preventing other mollusk species from using the rocks as their habitat.
7 Species Interaction
There are a number of ways that species within an ecosystem interact with each other. One of the more noticeable is through interspecific competition. Interspecific competition is when two or more species compete for limited resources. Maybe the most efficient and successful competitors are humans. We compete with many species for space, food and other resources. An example of this would be when part of a forest is clear-cut for the purpose of raising crops. This has two main effects as well as many others. First, it removes habitat from use by other species. Second, if a single crop is grown, then this monoculture is much less diverse than the vegetative species that were removed. What are some of the other negative impact examples on biodiversity can you think of?
Another way that species interact in ecosystems is through predation. There are numerous predator-prey relationships and your textbook has the example of sea otters that prey on clams and more important, sea urchins. Sea urchins in turn prey on the giant sea kelp. “The kelp forests are one of the most diverse ecosystems found in marine waters.” Please read the following sections in your textbook:
Core Case Study, page 102
Science Focus 5.1, page 105
Science Focus 5.2, page 114
Tying It All Together, page 117
8 Natural Population Dynamics; Biotic Potential and Environmental Resistance
A population is defined as a group of interbreeding individuals of the same species. The distribution of members of the population indicates they usually live in clumps or groups such as flocks of birds or schools of fish. Additionally, other characteristics are:
Concentration around resources,
Have better chance of finding resources,
Have protection from predators, and
Assist predators in getting a meal.
The general size of populations are governed by four variables:
Births
Deaths
Immigration
Emigration
The general equation for change in population size is:
Population Change = births + immigration – deaths + emigration
Population equilibrium is the balance between births and deaths.
Our discussion of species interaction is not complete without the topic of natural population dynamics. Most natural populations reside in a state of equilibrium or balance. An increase in the size of a population is also known by the term Biotic Potential. There are many reasons for a population to increase and decrease. Environmental Resistance factors can cause a population to decrease.
Biotic Potential
Reproductive rate
Ability to migrate (animals) or disperse (seeds)
Ability to invade new habitats
Defense mechanisms
Ability to cope with adverse conditions
Environmental Resistance
Lack of food or nutrients
Lack of water
Lack of suitable habitat
Adverse weather conditions
Predators
Disease
Parasites
Competitors
Environmental Resistance factors include such things as availability of light, water, temperature, space, nutrients, exposure to predators, or infectious disease. Otherwise called limiting factors that can limit the size of a population. There is actually a limiting factor principle where too much or too little of any physical or chemical factor can limit or prevent the growth of a population even if all other factors are at or near the optimal range of tolerance. Each population has a range of tolerance to their physical and chemical environment. This is represented in Fig. 5-15, pg. 112 that illustrates tolerance of a trout species to changes in water temperature. Species can be generalists or specialists. A generalist species like the raccoon has a broad niche while the Giant Panda is a specialist and has a narrow niche. Do you think that it is more beneficial to be a generalist or a specialist when it comes to survival?
Another population effect is that species have different reproduction patterns. Those species that have many offspring with relatively short lifespans are sometimes called r-strategists. This strategy works well for species like insects living in ecosystems that can suddenly change, like a rain-fed temporary pond. The second reproduction pattern is called the K-strategists in which there are small numbers of offspring that are longer lived, like elephants. They are usually species that care for their young until they are able to obtain resources along with the adults of the population. These strategists are more adapted to stable ecosystems.
When a population size drops below a level where the supportive interactions within the population are absent, then the species is at risk for extinction. Whatever individuals are more susceptible to disease and genetic variation is depleted to the point where extinction is almost inevitable when breeding fails. Individuals of the species may have depended on the protection and support of the pack or herd and when not available, the individual is unable to fend for itself. If a population size reaches the point at which it is less than the size needed to survive or recover, then that number of individuals is referred to as the critical number. Think back about the Northern white rhino’s predicament. Do you think that the Northern white rhino population has reached the critical number? What steps do you think humans should take to try and save the species?
9 National Population Dynamics; Population Growth Curves
Population growth curves are used to explain the condition of a population in equilibrium and a population that has grown beyond the capacity for the ecosystem to support further growth. Review the following population growth curves here, which contain the J-curve representing a population exceeding its’ carrying capacity and the S-curve representing population equilibrium.
Carrying capacity can be defined as the maximum population that a given habitat or ecosystem can support without degrading the habitat or ecosystem or a sustainable system. Habitat refers to where the species lives. Look at the J-curve. Do you think that this could apply to the human population? What do you think would happen to the human population if the Earth’s carrying capacity is exceeded? Can you give any examples in history when it appeared that the human population in a region experienced this exceedance?
10 Changing Environmental Conditions and Ecological Succession
What happens to biodiversity when there are forest fires, volcano eruptions or climate change? One example in 1988 was the forest fire in Yellowstone National Park that burned 165,000 acres. The outcome was that within weeks, grasses and other vegetation began sprouting from the areas. Apparent nutrients from the ash left behind fueled this growth and the large plant-eating animals like elk moved in to feed on the new vegetation. There was originally an expectation that recovery of biodiversity and possibly even enhancement of biodiversity would occur within 25 years after the fires. Guess what, it has been over 25 years! See if you can find out what the outcome to the biodiversity really turned out to be today in Yellowstone. There is another similar example that occurred in Washington State, although a different natural environmental change. Can you find out what this was and the outcome to biodiversity in this case as well?
These examples are sudden and cause environmental changes immediately. Usually these circumstances lead to what is called secondary ecological succession, which is illustrated in the graphic in Figure 5-12, page 110 of your textbook. Secondary ecological succession provides us with an example of how resilient a terrestrial ecosystem can be after a natural event like a forest fire. Ecologists call a more natural process with gradual change a primary ecological succession that results in gradual establishment of a terrestrial system with different species from bare lifeless areas without soil. This process occurs over hundreds or thousands of years and is illustrated in the graphic in Figure 5-11, page 109 of your textbook. Ecological succession is considered an “ecosystem service” but scientists today believe that such succession is just species trying to obtain the necessary resources to continue life and is an unpredictable process end result.
11 The Puffin Story
It is in humanity’s best interest to preserve biodiversity for reasons of our own survival. As part of this, there are efforts by humans to take steps necessary to bring native species populations back from near eradication or extinction. One example of how this was achieved has its’ roots in a biological concept first developed by Steven Kress, a National Audubon Society biologist in 1973. At a time just prior to the early 20th century, there was a healthy population of Atlantic Puffins in Maine. You can research the species characteristics on the Internet at: Atlantic Puffin
By 1900 the population of Atlantic Puffins had been devastated by uncontrolled hunting and the species was virtually gone from the region. There were laws passed to protect the Atlantic Puffins and sanctuaries set up, but the Puffins were already gone. Steven Kress developed a very controversial method at that time to try and restore the Puffin population. He promoted the elimination of a species of gull that competed with the Puffins. The idea was to re-introduce Puffins back into the ecosystem while temporarily eliminating some of the environmental resistance factors. He employed other tactics, together called Social Attraction, to “attract” Puffins from other regions. This included placement of decoys, fake eggs and sounds in the former Maine Puffin habitat. These methods have been used in other ecosystems to re-establish other bird species. Can you find some other examples? One of the main points of this story is for humans to be effective in protecting or re-establishing biodiversity in an ecosystem; then, sometimes it takes more than passing laws and setting aside sanctuaries. What do you think the status of the Atlantic Puffin population in Maine is today? What might be some remaining environmental resistance factors that the population must overcome these days?
12 Human Impacts on Biodiversity
In terms of the worldwide decline or loss of biodiversity, there are many causes and almost all are attributed to human activity. They reasons for decline in biodiversity include such activities as physical alteration of habitats, human population, pollution, and overuse of resources.
Physical alteration of habitats takes many forms. A brief description of these follows:
Click on each item below to reveal the description.
Conversion
This is where natural areas are converted to farms, housing sub-divisions and golf courses. It should be obvious, but loss of habitat results in a proportionate reduction in biodiversity through loss of the populations that required the habitat.
Fragmentation
Natural landscapes or habitats are (or were) well connected. Human landscapes that include highways, canals, and development fragment the natural landscapes and prevent migration.
Simplification
Humans tend to “clean up” natural habitats. Examples include when dead trees are removed from an area or when fallen leaves are raked up, bagged and taken elsewhere. You probably do this in your own yards and gardens.
Intrusion
Telecommunication towers and night-lights interfere with migratory birds. One pathetic attempt to resolve the aesthetic impact of cell phone towers is to design them to look like trees.
Human population impacts on biodiversity are found in all regions of the world, but mainly in more populated, less developed countries. The key to solving this would be to bring down the human population by slowing population growth. The next module will provide information that proves this to be a very difficult task. Pollution can be traced to industrialized regions and those with substantial energy generation. It does not appear to matter whether the countries are developed or less developed because both suffer from pollution that adversely impacts biodiversity. Nutrient enrichment of surface waters, oil spills, pesticides, human waste, acid rain and depletion of the ozone layer are all serious examples of damage to ecosystems and decline in biodiversity. Non-native, invasive or exotic species are all terms that relate to one of the most severe causes for loss of biodiversity. There are a tremendous number of these species, which can thrive in an ecosystem once introduced and can eliminate native species through predation and competition for space. Sustainable ecosystems depend on balance or equilibrium in their natural populations, but invasive species tend to unbalance ecosystems and cause them to be less sustainable. Overuse of resources usually refers to harvesting whales, fish or trees faster than they can reproduce. It also includes the trade and illegal trafficking in wildlife and products derived from wild species. Remember our endangered Northern white rhino species? What human activity do you think has been found to be partially responsible for the species demise?
13Value of Wild Species
The Puffin story bears out the need to put a high priority on protecting wild species and ecosystems. It is the biological wealth or biodiversity that comprises most of the ecosystem capital that sustains life and economic activity with goods and services. Humans are dependent on Earth’s biological wealth for food, materials and services. Wealth in terms of biodiversity is inseparable from a discussion of value in terms of wild species. The question is always raised as to what value a species has to humans?
There are two types of “value” that make it essential to preserve wild species. The first is instrumental value, which is usually the one that humans would identify with. It is the term relating wild species existence to some useful purpose to humans. There are many examples of this, such as honeybees, certain flowers with chemical extracts and fish species for the dinner table. Most humans would be able to identify the value of these species. The following characterizes some wild species instrumental value:
Click on each item below to reveal the description.
Sources for agriculture, forestry, aquaculture and animal husbandry
Example: Breeding plants in agriculture need “wild genes” to maintain traits for resistance to disease. Many more wild species could be brought into cultivation as food sources. Have you ever heard of a “seed bank”? Try to search the Internet for “Millennium Seed Bank”.
Sources for medicine and pharmaceuticals
Example: Somewhere around 3000 plant species have been discovered to have anti-cancer properties. One of these is the “Rosy periwinkle,” which contains chemical extracts used to produce two cancer drugs.
Sources for recreational, aesthetic and scientific use.
Example: Sport fishing, hunting, bird watching and photography. There has been a rise in “Ecotourism” especially valuable in developing countries as economic development such as diving in the Caribbean.
The second type of “value” of wild species is much more elusive to human understanding. Intrinsic value is the value of wild species for its own sake. It does not have to be directly useful to humans to have value. A number of ethical issues are involved with intrinsic value, but environmental ethics provides some insight. It is because humans have the ability to make moral judgements (right from wrong) that they have a special responsibility toward preserving the natural environment. Humans do not have the right to terminate or eradicate species since they have existed for thousands or millions of years longer than humans. Many of the worlds’ major religions support preservation of species and biodiversity in their teachings. Even if species have no demonstrable use to humans, it can still be argued that they have a right to continue to exist.
Protecting biodiversity will depend on human wisdom and values. It is wise for humans to protect the biological wealth that sustains so many of our needs and economic activities. Human technology and other social and cultural changes have assisted in expanding the carrying capacity of the Earth. Take a look at the attached graph of planetary carrying capacity. There still may come a time when the human population could reach the limits of the Earth’s goods and services or ecosystem capital to sustain human existence. Remember that human population growth is a global trend of concern along with all the associated negative environmental issues of consumerism and development. We will examine more of these issues in the next Module 5 and Chapter 6 in your textbook concerning human population growth.
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