UPSC Static Quiz – Environment : 18 May 2026

Solution: B

• Statement 1 is correct. Historical analysis and satellite imagery have confirmed that large-scale transformation of forest landscapes in the Western Ghats for commodity crops was a major driver of fragmentation during the 20th century. The southern ranges, including the Nilgiris and Anamalais, were extensively converted for tea and coffee plantations, while more recent expansions of rubber and cashew have impacted the northern parts. This process breaks large, contiguous habitats into smaller, isolated patches.
• Statement 2 is incorrect. Habitat fragmentation is detrimental to interior-forest specialist species. These species are adapted to the specific microclimatic conditions and resources found deep within large, undisturbed forests. Fragmentation reduces the amount of such “core” habitat and isolates populations, making them vulnerable to genetic bottlenecks and local extinction. Instead of increasing their population, fragmentation often leads to their decline and replacement by “generalist” species that can thrive in disturbed or edge habitats.
• Statement 3 is correct. The ‘edge effect’ is a key ecological consequence of fragmentation. When a forest is fragmented, it creates a large amount of “edge” habitat where the forest meets a different landscape (e.g., a plantation or road). These edges are exposed to more sunlight, wind, and temperature fluctuations than the forest interior. Studies in the Western Ghats have shown that this leads to significant microclimatic changes, including higher soil temperatures and desiccation (lower moisture levels). These altered conditions can affect nutrient cycling, seed germination, and the survival of species adapted to the cool, moist conditions of the forest interior.

Solution: A

• Statement I is correct. The impact of linear infrastructure is not just about the direct loss of habitat area. A highway might occupy a relatively small area, but its effect extends far beyond its physical footprint. It acts as a barrier, dissecting a large, contiguous habitat into smaller, isolated patches. This fragmentation effect can be ecologically more damaging for wide-ranging species or those with specific migratory routes than the loss of a similar-sized, non-linear patch of forest. For instance, a highway can isolate populations on either side, preventing genetic exchange and making them more vulnerable to local extinction.
• Statement II is correct. This statement provides the precise ecological reasons why linear infrastructure is so detrimental. These projects act as barriers that disrupt the natural movement, dispersal, and migration patterns of wildlife. For many species, crossing a busy highway is a high-risk activity, leading to significant roadkill mortality. For others, the barrier may be completely impermeable, effectively isolating populations. This genetic isolation can lead to inbreeding depression and a reduced ability to adapt to environmental changes. The statement accurately captures these dual impacts of fragmentation and direct mortality, which are the primary mechanisms through which linear infrastructure affects wildlife.
• Statement II provides a direct and accurate explanation for why the threat from linear infrastructure is considered particularly severe, as stated in Statement I.

Solution: B

• Statement 1 is correct. The Wildlife (Protection) Amendment Act, 2022, for the first time, introduced a definition for ‘invasive alien species’. It defines it as a species of animal or plant which is not native to India and whose introduction or spread may threaten or adversely impact wildlife or its habitat. The amendment empowers the Central Government to regulate or prohibit the import, trade, possession, or proliferation of such species, providing a much-needed legal tool to manage this threat.
• Statement 2 is correct. Lantana camara is one of India’s most widespread and problematic invasive species. It forms dense, impenetrable thickets that suppress the regeneration of native plant species. One of its significant ecological impacts is the alteration of fire regimes. The plant is pyrophytic (fire-adapted) and its dense, dry biomass acts as a heavy fuel load, leading to more frequent and intense forest fires. These fires can destroy native vegetation that is not adapted to such conditions, further facilitating the spread of Lantana.
• Statement 3 is incorrect. Prosopis juliflora (Vilayati Kikar) was introduced in arid regions for afforestation and to check desertification. However, it has become highly invasive. Far from restoring soil, its long taproots deplete groundwater tables significantly. Its leaf litter has allelopathic effects, meaning it releases chemicals that inhibit the growth of native plant species, thus reducing local biodiversity. It forms dense monocultures that outcompete native flora and are unsuitable as habitat for most native fauna. Therefore, it degrades the ecosystem rather than restoring it.

Solution: C

• Statement 1 is correct. Many invasive alien species are characterized as ‘pioneer’ or ‘colonizing’ species. They possess traits like rapid growth, high reproductive output, and effective dispersal mechanisms. While some can invade pristine, undisturbed ecosystems, they are particularly successful in establishing themselves in habitats that have been altered or degraded by human activities such as agriculture, logging, road construction, or pollution. Such disturbances create vacant niches and reduce competition from native species, providing an opportunity for the invaders to gain a foothold.
• Statement 2 is correct. This refers to the ‘Enemy Release Hypothesis,’ a key theory in invasion biology. In their native range, the population of a species is often kept in check by a suite of natural enemies, including predators, herbivores, parasites, and pathogens. When the species is introduced to a new region without these co-evolved enemies, it is ‘released’ from this biological control. This freedom from natural regulation can allow its population to grow exponentially and outcompete native species that are still subject to their own natural enemies.
• Statement 3 is correct. This is related to the ‘Biotic Resistance Hypothesis.’ It posits that ecosystems with high species richness and complex food webs are more resilient to invasion. The logic is that in a diverse community, most available resources (like nutrients, light, and space) are already being utilized efficiently by a wide array of native species. This leaves fewer empty niches for an incoming alien species to exploit. Furthermore, a diverse ecosystem is more likely to contain predators or competitors that can suppress the invader. Conversely, degraded ecosystems or those with low biodiversity (like monoculture plantations) offer less resistance to invasion.

Solution: D

(a) This scenario describes habitat loss, which is a primary driver of extinction but is not co-extinction. The Great Indian Bustard is directly threatened by the destruction of its habitat. It is not becoming extinct because another species it depends on has vanished.

(b) This scenario describes extinction due to disease. The global decline of amphibians, including many in the Western Ghats, has been linked to the chytrid fungus (Batrachochytrium dendrobatidis). This is a direct pathological cause of extinction, not a co-extinction event resulting from the loss of an associated species.

(c) This scenario describes mortality due to pollution or poisoning. The decline of vulture populations in South Asia is a well-documented case of the lethal effect of the veterinary drug diclofenac. While it represents a significant biodiversity threat, it is not co-extinction. The vultures are dying due to a chemical in their food source, not because the food source (cattle) itself has gone extinct.

(d) This scenario is a classic example of co-extinction. Many parasites are host-specific, meaning they can only survive and reproduce on or in a single host species. If the host species becomes extinct for any reason (e.g., overfishing, habitat loss), its dependent parasite assemblage, which cannot switch to another host, will also inevitably become extinct. This illustrates the cascading effect of extinction through tight ecological linkages. Another common example is the extinction of a specialist pollinator following the extinction of the specific plant it pollinates.