Biodiversity and Conservation

Learning Outcomes:

1. Understanding the importance of biodiversity at genetic, species, and ecosystem levels.
2. Awareness of the global species count and their distribution, particularly in India.
3. Grasping the factors influencing biodiversity, including species-area relationships and latitudinal gradients.
4. Insights into species extinction causes and the consequences for ecosystems.
5. Comprehension of biodiversity conservation strategies, including in situ and ex situ approaches.

Biodiversity

Biodiversity refers to the variety and variability of life on Earth at all levels, from genes to ecosystems. This term, popularized by Edward Wilson, represents the combined diversity at genetic, species, and ecosystem levels. To break it down, biodiversity exists at multiple levels:

1. Genetic Diversity: A species can exhibit considerable genetic variation across its distribution range. For example, the medicinal plant Rauwolfia vomitoria, found in different Himalayan ranges, shows genetic variation in the potency of the active compound, reserpine. India houses over 50,000 genetically different strains of rice and 1,000 varieties of mango.
2. Species Diversity: Diversity also exists at the species level. For instance, Western Ghats have a richer diversity of amphibian species compared to Eastern Ghats.
3. Ecological Diversity: At the ecosystem level, India displays great ecological diversity, with deserts, rainforests, coral reefs, wetlands, and alpine meadows, surpassing the diversity of Scandinavian countries like Norway.

The current rate of biodiversity loss poses a serious threat. If this continues, much of this richness could vanish within a few centuries.

Global and Indian Species Estimates

The International Union for Conservation of Nature (IUCN) (2004) records 1.5 million species globally, but the actual number might be much higher. Biologists estimate between 7 million species, with many still undiscovered, particularly in tropical regions. Among animals, insects dominate, constituting 70% of all species. The diversity of fungi surpasses that of fish, amphibians, reptiles, and mammals combined.

India, despite having only 2.4% of the world’s land area, supports 8.1% of global biodiversity, making it one of the 12 mega-diverse countries. With 45,000 species of plants and 90,000 species of animals recorded in India, estimates suggest many more are yet to be discovered.

Important Note: The actual number of prokaryotic species remains unclear, as conventional taxonomy methods cannot fully capture microbial diversity. Biochemical or molecular techniques may reveal millions more species.

Patterns of Biodiversity

Latitudinal Gradients: Biodiversity is not evenly distributed. Generally, species diversity decreases as one moves from the equator toward the poles. Tropical regions harbor more species than temperate or polar areas. For instance, Colombia, near the equator, has around 1,400 species of birds, while New York, at 41° N, has 105 species, and Greenland, at 71° N, has only 56 species. The Amazon rainforest represents the pinnacle of biodiversity, with 40,000 species of plants, 1,300 species of birds, 427 mammals, and over 1.25 million species of invertebrates.

Species-Area Relationships: Alexander von Humboldt observed a relationship between species richness and the area explored. As area increases, species richness also increases, though this relationship flattens after a point. The equation for this relationship is:

log S = log C + Z log A

Where S is species richness, A is area, Z is the slope, and C is the intercept. Typically, the value of Z ranges between 0.1 and 0.2. However, when analyzing larger areas like continents, the slope is steeper, sometimes reaching Z values of 1.2, indicating a greater influence of area on species richness.

Importance of Species Diversity in Ecosystems

Does Species Diversity Matter?: Ecologists have long debated whether more species make ecosystems more stable. A stable ecosystem should exhibit minimal variation in productivity, resilience to disturbances, and resistance to invasions by alien species. David Tilman’s experiments suggest that increased species diversity contributes to higher productivity and stability.

Important Note: The “Rivet Popper Hypothesis” by Paul Ehrlich offers an analogy: In an ecosystem, each species represents a rivet in an airplane. As species (rivets) disappear, the ecosystem becomes less stable, potentially leading to catastrophic failure if enough key species are lost.

Loss of Biodiversity

Biodiversity is being lost rapidly, largely due to human activities. According to the IUCN Red List, 784 species have gone extinct in the last 500 years, including notable examples like the dodo, quagga, and Steller’s sea cow. Extinction patterns are not random, with amphibians being particularly vulnerable. Over 15,500 species worldwide currently face the risk of extinction. Causes of extinction include:

1. Habitat Loss and Fragmentation: The destruction of habitats, particularly tropical rainforests, is the most significant driver of biodiversity loss. Tropical rainforests, once covering 14% of the Earth’s land surface, now cover only 6%. The Amazon rainforest, often referred to as the “lungs of the planet,” is being cut down at an alarming rate for agriculture and livestock.
2. Over-exploitation: When human need turns into greed, over-exploitation of resources occurs. Many species, like Steller’s sea cow and the passenger pigeon, have been driven to extinction due to over-harvesting. Today, several marine fish populations face similar threats.
3. Alien Species Invasions: Introducing species into new environments, either intentionally or unintentionally, often leads to ecological imbalances. The introduction of the Nile perch into Lake Victoria led to the extinction of over 200 species of cichlid fish. Similarly, the African catfish threatens native fish species in Indian rivers.
4. Co-extinctions: The extinction of one species often leads to the loss of others dependent on it. For example, the extinction of a host species can cause the extinction of its associated parasites.

Conserving Biodiversity

Conserving biodiversity is critical for various reasons. These can be categorized as:

1. Narrowly Utilitarian: Humans derive direct economic benefits from biodiversity, including food, firewood, medicine, and industrial products. Around 25% of modern pharmaceuticals come from plants. Exploring the genetic and molecular diversity of plants and animals offers potential economic gains, a practice known as bioprospecting.
2. Broadly Utilitarian: Biodiversity plays a significant role in ecosystem services, such as pollination, oxygen production, climate moderation, and pest control. The Amazon rainforest, for instance, contributes 20% of the world’s oxygen.
3. Ethical Reasons: Humans have a moral responsibility to protect other species. Every species, regardless of its economic value, has an intrinsic right to exist.

Important Note: Biodiversity conservation efforts aim to protect species at genetic, species, and ecosystem levels. Ensuring the survival of one species often requires safeguarding its entire habitat.

In Situ and Ex Situ Conservation

Conservation efforts can be divided into two approaches: in situ and ex situ.

1. In Situ Conservation: This approach focuses on protecting species in their natural habitats. Protecting an entire ecosystem, like a forest, ensures the survival of all the species within it. Biodiversity hotspots—regions with high species richness and endemism—are prioritized. Globally, 34 hotspots have been identified, including Western Ghats, Sri Lanka, and Himalaya in India. Though these areas cover less than 2% of the Earth’s land surface, they harbor 30% of all species. In India, 14 biosphere reserves, 90 national parks, and 448 wildlife sanctuaries have been established for conservation.
2. Ex Situ Conservation: When species face imminent extinction, they are conserved in controlled environments like zoological parks, botanical gardens, and seed banks. Advanced techniques like cryopreservation and in vitro fertilization help preserve species at risk of extinction.

MCQ: Which conservation method focuses on protecting species in their natural habitat?

Answer: In situ conservation.

In conclusion, biodiversity is vital for the health of ecosystems and the survival of humanity. Conserving biodiversity at all levels is essential, and both in situ and ex situ methods are necessary to protect the world’s natural heritage.