Biodiversity- Introduction
Biodiversity is a combination of two words, Bio (life) and diversity (variety). Biodiversity or biological diversity refers to the numbers, variety, and variability of living organisms and ecosystems. The term includes all terrestrial, marine, and other aquatic organisms. It also covers diversity within species, between species, as well as the variation among ecosystems. It is concerned also with their complex ecological intWhat is Biodiversity? Introduction, Types, Significance and Present biodiversity looser relationships.
Biodiversity has formed for a long period of time (about 3.5 billion years) on Earth. Many events have changed the biodiversity on Earth. Many species are no longer available now. Dinosaurs were present 65 million years ago but they are not available now. Species can be divided into three groups: endemic, endangered and extinct.
The species which are present in large numbers in an ecosystem is called the endemic species. A rich biodiversity means a wide variety of endemic species.
Endangered species are the species which are present in such amounts that if they are not protected, they will not be available anymore after some period of time.
The species which were present earlier in an area but are not found there anymore are called extinct species.Essential Types of Biodiversity
Species diversity refers to the number of plant and animal species present in a community or an ecosystem. It varies a great deal between ecosystems. For example, species diversity is very high in tropical rainforests and coral reefs and low in isolated islands. You will find a large number of different plants and animals in an ecosystem with high diversity,
- Genetic diversity- Genetic diversity means differences in genetic material (genes and chromosomes) of different organisms within a species or a population of an ecosystem.
- Species diversity - This type of biodiversity means the variety of species in a region. There are some areas which have a large number of species. These are called biodiversity hotspots. Such areas have high species diversity.
- Ecological diversity -This biodiversity is on a wider scale. There are large numbers of ecosystems on earth that have their species linked to each other based on their habitat. These can be forests, grasslands, deserts, mountains, rivers, lakes, seas etc. These areas form the ecological diversity.
Whittaker (1960) suggested the classification of biodiversity based on the community as a reference:
- Alpha Diversity (within ecosystem diversity) refers to the diversity of species within the same community or habitat.
- Beta Diversity (between community diversity) refers to the rate of replacement of species between two habitats or communities.
- Gamma Diversity refers to the diversity of habitats over the whole geographical area.
The following factors determine the degree of diversity in an ecosystem or community:
Habitat stress:- Diversity is low in habitats under any stress like harsh climate or pollution.
Geographical isolation:- Diversity is less in isolated regions like an island. If a species on an island disappears due to random events, it cannot be easily replaced. Organisms from the mainland have difficulties in reaching and colonizing the island.
Dominance by one species:- The dominant species consumes a disproportionate share of the resources. This does not allow many species to evolve and flourish.
Availability of ecological niches:- A complex community offers a greater variety of niches than a simple community and promotes greater diversity.
Geological history:- Old and stable ecosystems like rainforests that have not experienced many changes have high diversity. An ecosystem like the Arctic has undergone many changes and this does not allow many species to establish themselves.
Significance of Biodiversity
Biodiversity holds immense significance for mankind and adds value to human life in the following major ways:
Biodiversity is an integral part of the larger ecosystems of the earth. These ecosystems provide us with services that are of immense value. Life on earth, including that of human beings, would be impossible without these services. We are just beginning to appreciate their importance.
All the ecosystem services are provided by biodiversity. :
- Photosynthesis by trees and plants helps in climate regulation by absorbing carbon dioxide from the atmosphere.
- Many medicines products are derived from biodiversity, for example, Quinine to fight malaria is obtained from trees.
- Soil biodiversity plays a critical role in soil formation.
- Many industries like paper, timber, food processing etc depend directly on biological resources. We get these resources from different plants and animals. We get these from areas that have high biodiversity.
- Biodiversity provides energy and nutrient cycling across the trophic levels in ecosystems.
- Presence of biodiversity functioning of food chains and food webs and therefore maintains ecosystem stability. Removing any species from its community disrupts the food webs, energy and nutrient flows through the ecosystem.
Where is all the Biodiversity?
The majority of all species are in developing countries. 50-75% of all species are to be found in the tropical moist forests that account for just 6% of the land area.
A handful of soil in a tropical forest contains hundreds of species and more than a million individual organisms.
In the tropics and the sub-tropics, where we also find most of the developing countries, there was always evolutionary activity giving rise to rich biodiversity. Biodiversity is less in the colder Northern regions because the recurrent ice ages there slowed down the proliferation of life forms.
How many Species are there in this world?
We do not know exactly how many species inhabit this earth. Estimates range from 4 million to 100 million. Most of the species in the world are insects and microorganisms not visible to the naked eye.
So far about 1.8 million species (not including bacteria) have been identified, named, and catalogued. These include 270000 plant species, 45000 vertebrates, and 950000 insects. Roughly 10,000 new species are identified every year.
What is meant by the Extinction of species?
By extinction, we mean the complete disappearance of a species, that is, not a single member of the extinct species is found on Earth. It is an irreversible loss and is called biological extinction.
Before a species goes biologically extinct, it goes through stages of local and ecological extinction. Local extinction means that the species is no longer found in the area it once inhabited. It is, however, present elsewhere in the world. Ecological extinction means that so few members are left that the species can no longer play its normal ecological role in the community.
Extinction is the ultimate fate of all species. Since multi-cellular organisms evolved on Earth 570 million years ago, about 30 billion species have lived on this planet. Today, there are only about 14 million of them. This means that 99.9% of all species that ever lived are extinct!
Over the life of the earth, environmental conditions have been changing, gradually or rapidly. The large-scale movement of the continents and climate change are examples. When such changes occur, the affected species must adapt itself, move to a more favourable area, or become extinct.
What is Biodiversity Loss?
Biodiversity loss refers to the extinction of species from the planet. This not only reduces the species diversity but also the genetic diversity of Earth.
By extinction, we mean the complete disappearance of a species, that is, not a single member of the extinct species is found on Earth.
Extinction is the ultimate fate of all species. The evolutionary history of life suggests that many species have become extinct over time. As newer species evolve by natural selection, weaker ones gradually fade away. Although species richness has generally increased over time since the evolution of life on earth, yet in the last 500 million years, there have been a few episodes of large-scale decline of biodiversity too. These were the episodes of historical mass extinctions when more than half of all species on Earth disappeared in a very short duration of time. Such mass extinctions were caused by natural factors like - natural climate change, asteroid collisions, large-scale volcanic eruptions etc.
Measuring the Current Loss of Biodiversity
International organisations like World Wildlife Fund play a pivotal role in monitoring global biodiversity. The outcome of its efforts is the Living Planet Report which is released every two years. The Living Planet Index (an index for measuring global biodiversity) tracks the state of biodiversity by measuring the population abundance of thousands of vertebrate species around the world.
As per the latest Living Planet report 2018:
- Living Planet Index shows an overall decline of 60% in population sizes between 1970 and 2014.
- Current rates of species extinction are 100 to 1000 times higher than the standard rate of extinction in Earth’s history before human pressures became prominent
- Species population declines are especially pronounced in tropics, with South and Central America suffering the most dramatic decline of an 89% loss compared to 1970
- Freshwater species numbers have also declined with the freshwater index showing an 83% decline since 1970.
The report observes that the present level of biodiversity decline and degradation are not normal; they increasingly resemble some of the catastrophic extinctions in the geologic past. Therefore, the present biodiversity loss is being called as Sixth Extinction.
Threats to Biodiversity
The major cause for the decline in biodiversity is the following:
- Loss, degradation, and fragmentation of natural habitats, which includes deforestation and takeover of land for agriculture, industries, and human settlements
- Overexploitation of biological resources including overfishing and the commercial hunting and poaching of wildlife
- Pollution, in particular, the buildup of nutrients such as nitrogen and phosphorus on land and water
- Impacts of invasive alien species on Ecosystems
- Climate change and acidification of the ocean
Habitat Loss and Degradation
Human population is increasing day by day. This is destroying the habitat of different species. Forest ecosystems have a rich biodiversity. They are being destroyed due to the cutting of trees. Forests are cut to get land for agriculture and construction. For example, In the mangroves of Borneo, mangrove and peat-swamp forests have been cut. The area is used for oil palm plantations. This has destroyed the home of probosci's monkeys. They may become extinct in future.
Climate Change
The present climate change adversely affects biodiversity in multiple ways:
Climate change causes habitat loss for certain species like polar bears by accelerated melting of polar ice caps.
With changing climate, some species will need to adapt to modified environmental conditions at a fast rate. If they fail to do so, their populations come under increased stress. Chronic stress usually affects the reproductive success of species, eventually leading to population decline.
Temperature changes can confound the signals which trigger events like migration and reproduction, causing these events to happen at the wrong time. This will ultimately decrease biodiversity across regions.
For example, a small rodent, Bramble Cay melony, endemic to Australia has officially been recognised as extinct due to climate change by the Australian government in February 2019. It is the first mammal species officially recognised as extinct due to climate change.
Pollution
Environmental pollution impacts biodiversity both directly and indirectly.
Direct impact - Pollution makes the environment unsuitable for the survival of lifeforms. For example, the toxic chemical composition of oil spills kills marine organisms.
Indirect impact - pollution also affects the availability of food and reproductive success rates, thus reducing the species' population numbers over time.
Species Overexploitation
It can occur in two ways:
- Direct Exploitation - It may occur due to unsustainable hunting and poaching or over-harvesting either for subsistence or for trade. For example, illegal wildlife trade in diverse products like - rhino horn; tiger and leopard claws, bones, skin, whiskers; elephant tusks; pangolin scales; medicinal plants; timber etc. is a major cause of biodiversity loss globally.
- Indirect Exploitation - It occurs when non-target species are killed unintentionally. For example - sea birds, turtles and mammals are often killed as a bycatch in fisheries harvests.
Commercial hunting, poaching, and man-wildlife conflicts
The illegal world trade in rare and endangered species of plants, birds, and animals is estimated to be US$8 billion per year.
More than 37,000 plant and animal species are affected and these include rhinoceros, tiger, leopard, gorilla, butterfly, frog, tortoise, orchid, cactus, mahogany, etc. In addition, exotic pets and decorative plants are sold to collectors.
The poachers, mostly poor people in developing countries, depend on this trade for their livelihood. They collect specimens indiscriminately, killing young and old, male and female, often using very cruel methods. On average, for each animal captured alive, 50 others are killed. What is worse, most of the live animals that are captured die in transit.
The tragedy is that the poacher finally gets very little, most of the money going to the middleman. The country of origin also does not get any benefit, since no taxes or duties are paid. The country only loses its biodiversity for nothing.
Mass killing of animals for sport or for commercial purposes has driven some species like the blue whale into the endangered category.
In addition, man-wildlife conflicts are on the rise, leading to further loss of species. As human settlements encroach into forest areas and the traditional habitats of wild animals, direct encounters are unavoidable. The animals enter the villagers looking for food and injure or kill the residents. The villagers then are forced to kill the animals to protect themselves, their cattle, growing crops, and so on.
Introduction of non-native species or biological invasion
When a non-native species is introduced into an ecosystem and it has no predators, competitors, parasites, or pathogens to control its numbers, it can reduce or wipe out many local species. Hundreds of non-native species have been accidentally or intentionally introduced into coastal waters, lakes, and wetlands. Unintentional introduction occurs as stowaways in aircraft, through the ballast water of oil tankers and cargo ships, or as ‘hitchhikers’ on imported products like wooden packing crates.
In some cases, non-native species are deliberately introduced for getting some benefits. Initially, they may even be useful, but cause problems later by proliferating at the expense of local species.
In 1859, rabbits were introduced in Australia for sport shooting. Since the environment was favourable to them and there were no predators, their population exploded. They destroyed vast areas of rangeland, native wildlife, and sheep ranching. Finally, a disease virus was deliberately introduced to check their growth. We do not know what else the virus did!
Most species are affected by a combination of these reasons. An example is the decline of birds.
Consequences of Present Biodiversity Loss
The major consequences of biodiversity loss are the following-
- Loss of ecosystem services like photosynthesis, pollination, climate regulation etc. It will compromise the quality of life and overall well-being of man.
- Environmental problems are interconnected to one another. Biodiversity loss in the form of large-scale deforestation will exacerbate other environmental challenges like climate change and land degradation.
- Biodiversity loss in the form of deforestation or exploitative wildlife trade also leads to a rise in zoonotic diseases or zoonotic.
As per United Nations Environment Programme(UNEP), there have been dramatic reductions in ecosystems and biodiversity in the 20th century. Simultaneously, there has been an increase in the human population. Habitat destruction like deforestation and consumption of wildlife has increased the human-wildlife interface, thus exposing the human population to more zoonotic that spread from wild to humans. Statistics by the UNEP suggest that around 60 per cent of all infectious diseases in humans are zoonotic in origin.
Therefore, environmental challenges like biodiversity loss and ecological degradation have large ramifications for mankind and its well-being.
Frequently Asked Questions
Question: What is biodiversity?
Answer- It is the variety of all life forms of all types of ecosystems (terrestrial, aquatic, marine) on the planet.
Question: What are the different types of biodiversity?
Answer - The three types of biodiversity are-
- Genetic Diversity
- Species Diversity
- Ecological Diversity
Question: What is Biodiversity Hotspot?
Answer -A biodiversity hotspot is a region with a large number of endemic species. The name Hotspot was first given by Dr Norman Myers in 1988. Biodiversity hotspots are found all over the world.
Question: What is Biome?
Answer - It is a large geographical region with its predominant community of plants and animals.
Question: Concept of Megadiverse Countries
Answer - This concept was given by Conservation International in 1998. It refers to the world’s top biodiversity-rich countries. To qualify as a megadiverse country, a country must:
Have at least 5000 of the world’s plants as endemics.
Have marine ecosystems within its borders.
Question: What is the Endemic Species?
Answer - Those species which are restricted to only one geographic region and not found anywhere else.
For example, lion-tailed macaque is a primate species endemic to the Western Ghats of India. Nilgiri Tahr is a wild sheep species endemic to Western Ghats.
Question: What is the Umbrella Species?
Answer - These species have very large habitat needs upon which many other species depend. Umbrella species are different from keystone species. An umbrella species is determined based on its large habitat needs whereas a keystone species is determined based upon its role in maintaining the ecosystem structure.
For example, the Siberian tiger is an umbrella species with its territory stretching across Russia, China and North Korea.
Question: What is the Flagship Species?
Answer - These species act as a symbol for a habitat, environmental issue or campaign. Therefore, these can be mascots for the entire ecosystem.
For example, Tiger is a flagship species in India and is a symbol of wildlife conservation. Polar bears are flagship species of climate change challenges for biodiversity.
Also, Check out - Biodiversity Conservation | In-Situ & Ex-Situ Conservation