This presentation covers IBESS Topic 3.3, Threats to Biodiversity, under the main Topic 3 of Biodiversity and Conservation. Recall from Topic 3.1 that the total number of species on Earth is estimated to be about 8.7 million, with about 6.7 million on land and 2.2 million in the oceans. However, some estimates of the numbers of species on Earth stretch to a hundred million. million species.
Note that only about 1.2 million of all these species has been formally described. What are the techniques to determine the number of species on earth and why do the numbers vary so greatly? In the more than 250 years since Swedish biologist Carl Linnaeus began the science of taxonomy, 1.2 million species have been identified and classified. Less than 15% of Maura's new total from the previous slide. At this pace, it would take another 480 years to complete the job of recording all species.
Scientists make predictions using mathematical modeling. They compare what is known with their modeling to verify validity of the approach. It's challenging because science might disagree or change their mind about classification. Furthermore, as we've discussed in class, extinction is ongoing. while new species are also being formed remember the new species the big finch of the galapagos or the underground mosquitoes of london furthermore there are difficulties in estimating the number of species our understanding of the number of species on earth is affected by a lack of finance for scientific research with habitats and groups being significantly under reported because some species are very small and difficult to find like bacteria and insects or some live in remote habitats like deep oceans and deep soil and high canemies it takes a huge effort to catalog all the species huge quantities of time and money are required to meet this task let's switch gears slightly to focus on the topic extinction recall that extinction is the process by which a species genus or family becomes extinct meaning it no longer exists or lives in the world.
99% of all species that have been on Earth no longer exist. Extinction is forever. For example, this little melami was endemic to the tiny island of Bramble Cay, Australia.
It has been officially declared extinct as of 2016. It's extinction due to a rising sea levels and subsequent loss of habitat. You need to be able to discuss the estimates of rates of extinction over time. Extinction estimates prior to people was about one extinction per 1 million species per year which is about 1 ten-thousandths of a percent.
Extinction today however occurs at a rate of 100 extinctions per million species per year. Other estimates claim 30,000 to 60,000 extinctions per year out of all species alive today. This is a hundred to ten thousand times greater than the background extinction rates or the extinction rates occurring before people. If the extinction rate is one percent, then 20 percent of all the world's species will be gone by 2030. That's your lifetime. And recovery of that biodiversity loss would take millions of years.
And this is the reasoning behind the idea that we are currently in the sixth great... mass extinction. The International Union for the Conservation of Nature or the IUCN has been keeping a record of species extinction since 1500. Their studies have generated extinction rates of one hundredth of a percent which is 100 times greater than background extinction rates before people.
This image was pulled from the IUCN site in February 2019. It shows estimates for the percent of species on Earth today that are currently threatened with extinction due to human activity. 40% of amphibians, 25% of mammals, 34% of conifers, 14% of birds, 31% of sharks and rays, 33% of coral reefs, and 27% of crustaceans are currently threatened with extinction due to human activity. The IUCN data also shows that extinction rates have been increasing in recent years. Extinction rates are not linear.
because species, habitats, and biodiversity are not evenly distributed equally through the earth. As you know, hotspots contain far greater quantities compared to other regions of earth. Furthermore, when half of a habitat is lost, animals and plants remain in the other half.
Their numbers are fewer there, but they are there. Only when nearly all of that habitat is lost will extinction rates increase rapidly. Look at this example of the Bornean Amazon being destroyed in favor of palm oil plantations. There are still species over here, but when the desire for palm oil increases and this habitat is further destroyed, there will be a rapid increase in extinctions. In other words, it's not going to be linear.
There are two causes of extinctions, natural causes, non-human, and human causes. There are many natural events that contribute to biodiversity loss and extinctions, such as volcanic eruptions, earthquakes, floods, fires, hurricanes, drought, meteors, glaciers, and ice age, and competition and predation. But this graph shows us that there is a correlation between human population and extinction.
What activities do humans do to cause this extinction rate? This acronym might help you to remember. HIPPO. H is for Habitat Destruction and Fragmentation. I is for Introduced Species.
P is for Pollution. P is for Practices of Agriculture. And O is for Overhunting. H. Habitat Destruction. Destruction of habitat is reducing the quality of available habitat, for example, through logging, agriculture, and sewage.
Fragmentation of a habitat is splitting a single large contiguous system into many disconnected areas. For example, putting a road through a wilderness area or building a dam across a river or this road through the Amazon. Loss of habitat is the disappearance of an entire habitat. For example, by paving natural area for building sites, converting prairies to farmland or residential subdivisions. I is for invasive species.
otherwise referred to as alien, exotic, or non-native species. Organisms that are living in an environment outside of their normal range or natural environment. Many are transported by accident. Some are imported for biocontrol. In other words, trying to intentionally control another problem species population.
The characteristics of invasive species are that they are fast growing. They live in a wide range of environments. They are usually harmful to the environment and they out-compete native organisms for local food sources, leading to extinction of native organisms. Let's highlight just a few of the 50,000 invasive species of the United States.
Asian carp, kudzu, and starlings, as well as the classic examples from Australia of rabbits and cane toads. Introduced to control weeds and parasites in aquaculture, flooding allowed the Asian carp to escape into the Mississippi River and its tributaries, where they quickly became many carp. Asian carp have been crowding out native fish, compromising water quality, and killing off sensitive species that are a strong threat to the Great Lakes in the northern United States. The image here at the bottom is of an Asian carp out of the Great Lakes. Kudzu is found throughout Asia and was introduced at the Centennial Exposition in Philadelphia in 1876, where gardeners marveled over its fast-growing tendencies and strong root system.
By the early 1900s, use of kudzu was already widespread. The Soil Conservation Service even hired hundreds of men to plant kudzu for erosion control in the 1930s. By the 1940s, the government was paying farmers in the South to plant the vine by the acre. All of the reasons people were originally attracted to this creeping vine make it an incredibly damaging invader. Known to grow 30 centimeters a day in the summer season, Kutsu vines grow up to 30 meters long and can quickly smother trees, houses, power lines, and anything else that stands in the way.
Tolerant to both drought and frost, its hardiness allows it to remain dominant and outcompete other plants. Forests can be completely destroyed by this vine. completely overrun by the plant in as little as two or three years, resulting in lower biodiversity and productivity.
On March 6, 1890, a New York pharmaceutical manufacturer named Eugene Shieflin released approximately 60 starling birds into the wild. They survived the winter and began to breed and spread and breed some more. They are genetically fit to survive.
Their binocular vision combined with their open bill probing ability means that starlings can find insects in colder climates better than other birds which means that starlings do not have to migrate to warmer climates in the winter which means that they can take the best nesting holes during the breeding season. Starlings will bully other birds kicking bluebirds, flickers, and woodpeckers out of their nest. They can consume whole fields of wheat and transmit avian animal and human diseases.
Today, starlings are blamed for agricultural losses of up to $800 million annually in the United States, as well as being implicated in a number of deadly plane crashes. Rabbits were introduced to Australia in the 1800s by European settlers. This quotation indicates how unsuspecting people can be of their actions regarding introduction of alien species into the environment.
As quoted by Thomas Austin, the introduction of a few rabbits could do little harm and might provide a touch of home in addition to a spot of hunting, he said when he released 24 rabbits. Free from diseases and facing relatively few predators in a modified environment, the wild populations grew rapidly. They quickly spread across two-thirds of Australia with devastating impact.
The rabbits compete for food and shelter with native animals, but also environmental harm comes from how they graze because they help maintain feral predators. Rabbits have clearly contributed to the decline or loss of at least four native species in Australia. A classic example of biocontrol is the cane toad.
In 1937, 102 cane toads were leased in Australia's sugar cane plantations to control beetle populations that were eating the sugar cane crops. By 1938, approximately 60,000 cane toads left sugar cane fields for more natural habitat eating, eating all of the majority of insect populations and out-competing native amphibians for food. They can grow up to 45 centimeters and 2 kilograms and can eat anything. The population has mushroomed to over 1.5 billion.
Here you see toads collected and backpackers that in exchange for helping capture cane toads have been given a visa extension in Australia. That's how desperate things have become in an effort to control the cane toad population. Moving away from invasive species, P is for pollution. Of course the toxins we add to the environment lead to a loss or degradation of habitat and destruction of species.
Hundreds of marine species are threatened by plastic pollution alone. P. Practices of Agriculture Farming causes habitat loss and reduces biodiversity because of monoculture, the farming of only one crop on a large scale, because of pesticides, which are often lethal to many non-pest species, and because of herbicides. which are lethal to species other than the weeds. Finally, O for overhunting.
Collecting and harvesting wild populations. If unregulated, it can diminish local populations or even drive some to extinction. Some examples include the Tasmanian tiger, the dodo, the passenger pigeon, and more recently, the North American sea mink.
The tragedy of commons is that individuals who behave for the good of their groups lose out in the struggle for existence with more self-serving individuals, resulting in over-exploited resources and other tragedies of non-corroboration. Thus, there is a tension between the common good and the needs of the individual. If it belongs to all, we tend to exploit it, right? Here, everything's belonging to all. and so you can see it's no longer green.
But when it's divided up and we all have specific ownership, we tend to take more care. For example, the oceans belong to everyone. Therefore, everyone tries to get all they can from them, resulting in the fact that overfishing is a problem today.
The current rate of catch is unsustainable. You need to be able to describe and explain the factors that make a species more or less prone to extinction. These are the factors that are used to determine conservation status of a species.
I will now discuss several characteristics of what makes a species vulnerable or prone to extinction. A specialized niche makes a species more prone to extinction. For example, the panda that feeds exclusively on bamboo or the koala that feeds exclusively on eucalyptus are species prone to extinction.
because of their extremely specialized niches. Organisms that have a low reproductive potential, typically the K strategists, are more likely to go extinct. The blue whale produces a single calf every two to three years, and the mountain gorilla produces maybe two to six offspring in a lifetime. Species must be able to reproduce to survive, and low reproductive rates make the potential for survival more difficult.
in a scenario of rapid environmental change. Organisms that have a narrow distribution or are rare may be more likely to go extinct. For example, this midge, a small wingless fly, is the only insect endemic to Antarctica. Also, these lemurs are endemic to the island nation of Madagascar. Again, having a limited range of distribution makes the species more prone to extinction.
Organisms that require a large territory are also more prone to go extinct. The female Bengal tiger, for example, would need a 20 square kilometer area and the male tiger requires an even larger territory that covers 60 to 100 square kilometers. Most of tigers habitats also need to be near a body of water such as a lake, pond, or river. Again, such prime real estate is becoming increasingly scarce as humans take more and more habitats for their own needs.
Organisms that are migratory may also be more likely to go extinct. Species with fixed migratory patterns like the wildebeest, the monarch butterfly, and the humpback whale rely on at least two different habitats for success. This makes migratory species more prone to extinction because if either habitat is destroyed or the migratory pathway is interrupted, Those species are at risk. Organisms that have ground nests may be more likely to go extinct because their eggs are more vulnerable to predators. This is a particular issue as non-native species arrive prepared to eat anything they can get a hold of.
Species that feed at a higher trophic level are more prone to extinction. Animals that feed higher up on the food chain are more dependent on multiple trophic levels below. They also tend to be rare.
Think about the pyramid of numbers, and they are more susceptible to biomagnification as non-degradable toxins increase in magnification up the food chain. Organisms that are valuable economically may also be more likely to go extinct. If a species is seen as valuable for food, medicine, or cultural interest, they are more prone to extinction because they will be hunted for their perceived value. The cultural interest in elephant tusks and rhino horns is not only a factor in the population's interest in food, but also in the population's interest in food. has driven these species towards extinction.
And of course, organisms that are vulnerable to the pollution that we put into the environment may also be more likely to go extinct. The rainforest itself is vulnerable to extinction. It contains 50% of Earth's known species, and most species have specialized niches.
Humans disrupt the rainforest environment for logging, and changing one entire population. part of the ecosystem alters the entire web of relationships. Breakdown of the rainforest will likely lead to the extinction of 10% of world species in 25 years. And of course, you know, regeneration rate is slow. The International Union for Conservation of Nature, or the IUCN, has a red list that puts species into categories based on how threatened the species are.
The IUCN seeks to provide a system that can be applied consistently and to improve evaluation of different factors which affect the risk of extinction. The basis for estimating how threatened a species might be comes from several sources of data. Population size.
How many of this species exist? Reduction in population size. How fast is the population decreasing?
Numbers of mature individual. These are past their reproductive years and may lead to further decline. Geographic range and fragmentation.
Wide range makes the species less likely to be threatened. Fragmented habitat reduces interbreeding populations. Quality of habitat.
Degraded habitat supports fewer individuals. These are the categories of extinction classified by the IUCN. with these three categories being of most concern to conservationists. I will provide an example for each of the main categories of Red List, as obtained directly from the IUCN. If a species is extinct, there is no reasonable doubt that the last individual has died.
It's been determined after exhaustive surveys of the animal's known range and expected habitats. The golden toad... was classified as extinct in 2008 due to invasive species, airborne pollutants, and the effects of climate change.
Extinct in the wild. Members of this species survive only in captivity or as artificially supported populations far outside of their historical geographic range. The Oryx doma was classified as extinct in the wild because the species since then has only existed in specified farms. Hunting and livestock farming and ranching are its main threats.
critically endangered. These species are considered to be facing an extremely high risk of extinction in the wild. The elongated tortoise was classified as critically endangered in 2018. Its threats include agriculture, aquaculture, roads and railroads, hunting and trapping of terrestrial animals, as well as gathering of terrestrial plants and pollution.
Endangered species are unlikely to survive if causal factors continue operating. These species are identified because of their drastically reduced populations and 50-70% loss of their habitat in the previous 10 years. The Jefferies spider monkey was classified as endangered and its main threats are agriculture, hunting, logging, and wildfires.
A species classified as vulnerable has a very high risk of extinction. To be classified as vulnerable, There is a 30 to 50 percent reduction in their population in the previous 10 years. The Indian rhinoceros has been classified as vulnerable due to residential and commercial development, agriculture, transportation corridors, hunting and civil unrest, dams and water management, invasive species, and the effects of climate change.
Species classified with least concern are pervasive and abundant. The Arabian horned lizard has a status of least concern with its largest threat. being hunting and trapping. To recap the contents of this movie, numbers of species and biodiversity are estimated using mathematical modeling, which has limitations, such as classification problems and the facts that extinctions are ongoing and new species are being formed.
The causes of extinction are natural, such as volcanoes, earthquakes, floods, etc., or they are human-caused. Remember, HIPPO. H for habitat destruction, degradation, or fragmentation. I for invasive species.
P for pollution. P for practices of agriculture. And O for overhunting.
The tragedy of commons, or the conflict between acting for the greater good versus the individual, results in the exploitation of our resources. Factors that make species prone to extinction, including having a spatialized niche, low production rate, narrow distribution, large territory, migratory patterns, ground nesting, higher trophic level, economic value, or being vulnerable to pollution. And the IUCN classifies extinction status based on population size, reduction in numbers, geographic range, and quality of habitat. This ends the movie for IBESS topic 3.3, Threats to Biodiversity. The slides are adapted from William Green's presentation from the site from The Amazing World of Science with Mr. Green.
The Amazing World of Science is licensed under a Creative Commons Attribution International license. Additional insight was obtained from Mr. Dave Hoover's movie presentations at Hoover's YouTube channel. Both of these provide additional resources for study and learning.
Another resource for you is your IBESS textbook. whether in hardback form or online, such as Cognatee. Thanks for listening.