Introduction to Biodiversity
This article deals with ‘Introduction to Biodiversity – UPSC.’ This is part of our series on ‘Environment’ which is an important pillar of the GS-3 syllabus. For more articles on Science and technology, you can click here
According to the Convention on Biodiversity (CBD), Biodiversity is the variability among the living organisms, inter alia, terrestrial, marine and other aquatic ecosystems. It also includes diversity between species and within species.
Genetic Diversity, Species Diversity and Ecosystem Diversity
There are three levels of biodiversity, i.e. Genetic diversity, Species diversity and Community/Ecosystem diversity.
1. Genetic Diversity
Genetic diversity is the diversity that is found at the level of genes. Genetic diversity is the differences in the genetic make-up within a single species.
Some points to note about Genetic Diversity
- The greater the genetic diversity, the more capable are the genes to face different threats, therefore increasing the chances of an organism surviving in adverse conditions.
- India has more than 50,000 different varieties of rice. But these rice varieties have faced the onslaught of monoculture promoted by the Green Revolution resulting in more diabetes in the Indian population.
- Generally, the tropics have greater genetic diversity.
2. Species Diversity
Species diversity denotes the number of species per unit area. It signifies the richness of species in a given habitat.
Some points to note about Species Diversity
- The Eastern Himalayas are especially rich in species biodiversity because high temperature, humidity and rainfall promote different biogeographic zones, causing the development of flora and fauna in these biogeographic zones.
- Species diversity is also greater in the tropics because of the following reasons.
- High heat and humidity which is optimum for metabolic activities
- These regions have been climatically stable.
- As weathering and erosion are greater in the tropics, the soil mantle is greater. Therefore, floral and faunal diversity is high.
- Generally, smaller islands have more endemism than species richness. In other words, there will be unique species on the islands, but different varieties aren’t found on the islands. Therefore, the general rule is that islands are poorer in species richness than the mainland areas.
- Most of the islands are unique in the way that they have a high degree of endemism, but the species are threatened because an invasive alien species can easily colonize the island.
3. Ecosystem / Community Diversity
Ecosystem Diversity refers to the ecosystem level diversity due to the diverse niches, trophic levels and ecological processes such as nutrient cycles, energy flow etc.
Alpha, Beta and Gamma Biodiversity
1. Alpha Biodiversity
- Alpha biodiversity is measured by counting the number of species within a particular area, community or ecosystem.
2. Beta Biodiversity
- Beta biodiversity is the comparison of biodiversity between ecosystems. It is the change in the number of species between ecosystems.
3. Gamma Biodiversity
- It is the measure of the overall biodiversity of the total landscape or geographical area.
Points to remember
- Walter Rosen coined the term biodiversity in 1986.
- Terrestrial biodiversity is 25 times more than that of ocean biodiversity.
- Terrestrial biodiversity is highest near low latitudes or the equator. The reason behind this is the warm climate & high primary productivity.
- Marine biodiversity is highest in the Western Pacific Ocean & in the mid-latitudinal band, where surface temperature is highest.
- Biodiversity declines to move northwards from the tropics. For example, northernmost regions such as Tundra and Taiga regions in Canada, Northern Europe and Alaska have less than 12 species.
Do you know? International Biodiversity Day
22 May is celebrated as International Biodiversity Day to commemorate the adoption of the text of the Convention of Biological Diversity at a conference in Nairobi, Kenya
- The theme for IBD 2021: We’re part of the Solutions
- The theme for IBD 2020: Our solutions are in nature
Ecosystem Services are the processes by which the environment produces benefits useful to people akin to economic services. E.g.
- Provision of clean water & air
- Pollination of crops
- Mitigation of environmental hazards
- Preventing soil erosion
- Cultural services such as cultural advancement of people (like inspiration for music, painting etc.), recreation and building of knowledge
Insects and Ecosystem
- Insects play an important role in sustaining life and food security by acting as pollinators and natural recyclers.
- The population of insects has been reduced at the rate of 9% in the previous three decades due to various reasons like the introduction of broad range insecticides like DDT, climate change, honey hunting etc. For example, the US lost half of its butterfly population due to the introduction of DDT in the 1940s.
- It is important to arrest this development. Otherwise, it will imperil the world food supply as pulses, oilseeds, and fruits depend on pollination.
Inter-Governmental Platform On Biodiversity and Ecosystem Services (IPBES)
- It was created in 2012
- Its secretariat is situated in Germany and is administered by the UN.
Causes of Biodiversity loss
Biodiversity is being lost at an unprecedented scale, as pointed out by WWF’s Living Planet Report (2018), which stated that between 1970 and 2014, 60% of the world’s vertebrate population (animals with a backbone) was wiped out by human activity.
1. Habitat destruction or fragmentation
- Habitat destruction and fragmentation are happening due to the following reasons
- Conversion of land for agriculture
- Land use for construction purposes
- Damage to coastal and marine systems for the construction of ports and infrastructure
- The aptest example of habitat loss is the Amazon rainforest, also known as the “Lungs of the planet”, which is destroyed and being replaced by agriculture and human settlements.
- Habitat fragmentation leads to biodiversity loss because mammals and birds require a large minimum territory to sustain their population.
- Nutrient loading into the ecosystems leads to Algal blooms and Eutrophication.
- Air pollution has a detrimental effect whole ecosystem.
3. Invasion of Exotic Species
- Invasive species are introduced – intentionally or unintentionally – to an ecosystem in which they don’t naturally appear & which threaten habitats, ecosystems or native species.
- They become invasive due to high reproduction rates & absence of natural predators to control their population.
- Examples include
- Tilapia fish: It was introduced in the inland waters of Kerala in 1952 from the eastern coast of South Africa because of its higher productivity. But the fish became invasive, resulting in the extinction of native species.
- Nile Perch: The fish was introduced in Lake Victoria, which grew at an exponential rate and led to the extinction of more than 200 species.
- Due to population overgrowth, humans are overexploiting biological resources. E.g. due to increased demand for fish, 50% of world commercial fisheries are fully exploited, and 25% are overexploited.
- Species such as Dodo and Steller’s sea cow have already become extinct in the last 200-300 years due to over-exploitation by humans.
- Animals are hunted for commercial exploitation as well as for sport.
- For example, in 2021, Pakistan gave a permit to Dubai Royals to hunt Houbara Bustard Bird (status: vulnerable) for money.
6. Climate Change
Climate change and global warming have led to the following detrimental impacts on biodiversity
- Species redistribution
- Effect on the timing of reproduction & migration.
- Increased frequency of pest outbreaks and forest fires.
- Co-extinction is the process in which the extinction of one species leads to the extinction of another species, which has a mutually beneficial relationship with the extinct species. For example, the extinction of fish leads to the extinction of parasites that feed on the host fish.
- The most famous example of co-extinction is that of the Calvaria tree and Dodo (extinct bird of Mauritius Island). Both were mutualistic associated as Dodo helped germinate tough endocarp of the seeds of the Calvaria tree through its digestive juices and stones in the bird’s gizzard. Thus the extinction of Dodo led to the extinction of the Calvaria tree as well.
8. Use of Hybrid Seeds
- Hybridization between native and non-native species and subsequent loss of native species.
9. Natural disasters
- Natural disasters like tsunamis, forest fires, earthquakes, volcanic eruptions etc., also cause irreparable damage to the region’s biodiversity.
10. Jhum cultivation
- Jhum cultivation involves slashing down and burning the natural vegetation to prepare the land for cultivation. The farming is done on the plot for 2 to 3 seasons, after which the tribal farmers move to another plot due to the reduction of the fertility of the given land.
The loss of biodiversity is dangerous for the whole ecosystem. The ‘River Popper Hypothesis‘ by ecologist Paul Ehrlich beautifully explained the perilous impacts of biodiversity loss. He compared the species in an ecosystem with the rivets in the aeroplane’s body.
- If some of the rivets on the body are removed, nothing serious happens to the aeroplane.
- But if rivets beyond a certain number are removed, the whole aeroplane will fall apart.
- Which rivet is removed matters as well. If the key rivet is removed, the whole aeroplane can collapse with the removal of a single rivet.