Enforcement Officer / Accounts Officer (EO/AO) 2020 recruitment test, advertisement 421. Transcribed from the Commission's own booklet (series A, NMJX-U-GTA); answer as per the official UPSC final answer key. This question is in Part B. Answer last reviewed 24 August 2026.

Which one of the following is not a consequence of deforestation ?

(a)Increased groundwater table
(b)Decreased biodiversity
(c)Increased soil erosion
(d)Decreased rainfall

Answer

Why

Correct — A, (a) Increased groundwater table. The emphasised 'not' asks which listed effect deforestation does NOT produce, and a rising water table is the one that runs the wrong way. A forest recharges groundwater rather than draining it: the canopy breaks the force of falling rain so that it soaks in instead of running off, the litter layer on the floor holds water like a sponge, and the root network opens channels down which water percolates into the soil and on to the aquifer. Strip the trees and rainfall arrives on bare, compacted soil, runs off the surface as sheet flow, and reaches the streams in a flood instead of the aquifer as recharge. Less infiltration means less recharge, so the water table FALLS — which is why wells and springs in deforested catchments tend to dry up earlier in the season and have to be deepened. The other three options are all textbook consequences of clearing forest: habitat loss cuts biodiversity, unprotected soil erodes, and reduced transpiration cuts the moisture returned to the atmosphere and so reduces local rainfall.

Why the others are wrong

(b)Decreased biodiversity — This IS a consequence of deforestation, so it cannot be the exception the question wants. Forests hold a disproportionate share of terrestrial species, and clearing them destroys habitat, breaks continuous forest into isolated fragments that small populations cannot cross, and removes the food plants and nesting sites specialised species depend on. Fragmentation is the part students underweight: even where total forest area falls only a little, cutting a block into pieces raises the edge-to-interior ratio, dries out the interior and pushes out species that need deep forest. Loss of biodiversity is the single most cited ecological cost of deforestation.
(c)Increased soil erosion — This IS a consequence, so it is not the answer. Tree roots bind soil particles together and the canopy plus leaf litter absorb the impact of raindrops that would otherwise detach soil grains. Remove them and the topsoil — the thin fertile layer that took centuries to build — is carried off by runoff and wind. On slopes this shows as gullying and landslips; downstream it shows as silt filling reservoirs and raising riverbeds. Erosion is also the mechanism that links deforestation to flooding, because a catchment that has lost its soil sponge delivers its rain to the river far faster.
(d)Decreased rainfall — This IS a consequence and so cannot be the exception. Forests pump large volumes of soil water back into the air through transpiration, and that moisture feeds cloud formation and rainfall over and downwind of the forest — the recycling that keeps large humid forests wet. Cut the forest and transpiration collapses, while the bare, lighter-coloured surface reflects more sunlight and heats differently, weakening the convection that lifts moist air. Both effects reduce local and regional rainfall. This option is the one candidates hesitate over, because the link runs through the atmosphere rather than through the soil, but it is standard textbook material.

Concept

Deforestation is best understood through the four systems a forest regulates, because every consequence in an exam list belongs to one of them. WATER: the canopy intercepts rain, the litter layer stores it and roots channel it downward, so a forested catchment converts rainfall into slow infiltration and steady baseflow; removing the forest converts the same rainfall into fast surface runoff, giving floods in the wet season, dry streams in the lean season and a falling water table. SOIL: roots bind and the canopy shields, so clearing exposes topsoil to raindrop impact, runoff and wind, producing erosion, gullying, loss of fertility and siltation downstream. In dry regions the end point of that process is desertification. BIODIVERSITY: forests are the habitat for a large share of land species, and clearing and fragmenting them drives local extinctions. CLIMATE: forests transpire moisture that returns as rain, shade and cool the surface, and lock carbon in wood and soil, so their removal reduces rainfall, raises local temperature and releases carbon dioxide. Read against that framework, three of this question's options fall straight out of it and only the first contradicts it.

Environment items on the general ability paper are usually testing whether a candidate can reason about direction of change rather than recall a fact. Every option here names a real, well-known effect; what distinguishes them is the SIGN. 'Increased groundwater table' is built to catch the loose association 'trees drink water, so fewer trees means more water left underground'. That reasoning ignores where groundwater comes from — recharge through the soil — and treats an aquifer as a tank that trees drain. The habit the question rewards is asking, for each option, which way the arrow points and by what mechanism.

Key facts

Forests aid groundwater recharge: canopy interception, leaf litter and root channels together increase infiltration and reduce surface runoff.
Deforestation therefore LOWERS the water table in a catchment; wells and springs run dry earlier in the season.
Deforested catchments deliver rain to streams quickly, producing flash floods in the rains and low flows in the dry months.
Tree roots bind topsoil and the canopy absorbs raindrop impact, so clearing increases soil erosion, gullying and downstream siltation.
Forests recycle moisture through transpiration; losing them reduces local and regional rainfall.
Forests store carbon in biomass and soil, so clearing and burning them releases carbon dioxide and adds to global warming.
Habitat loss and fragmentation are the main routes by which deforestation reduces biodiversity.

Four systems a forest regulates — three options follow, one runs backwards

(a) Increased groundwater table — the one that runs the wrong way→A forest RECHARGES groundwater: the canopy breaks the force of falling rain so that it soaks in instead of running off, the litter layer on the floor holds water like a sponge, and the root network opens channels down which water percolates to the aquifer. Strip the trees and rainfall arrives on bare, compacted soil, runs off as sheet flow, and reaches the streams in a flood instead of the aquifer as recharge. The water table therefore FALLS, which is why wells and springs in deforested catchments dry up earlier in the season and have to be deepened.

WATER, the system that option (a) belongs to→A forested catchment converts rainfall into slow infiltration and steady baseflow; a cleared one converts the same rainfall into fast surface runoff — flash floods in the wet season, dry streams in the lean season.

SOIL — option (c), increased erosion→Roots bind soil particles together, and the canopy and leaf litter absorb the impact of raindrops that would otherwise detach soil grains. Remove them and the thin fertile topsoil, built over centuries, is carried off by runoff and wind: gullying and landslips on slopes, silt filling reservoirs and raising river beds downstream. In dry regions the end point of that process is desertification.

BIODIVERSITY — option (b), decreased→Forests hold a disproportionate share of terrestrial species. Clearing destroys habitat and breaks continuous forest into isolated fragments that small populations cannot cross, removing the food plants and nesting sites that specialised species depend on.

CLIMATE — option (d), decreased rainfall→Forests pump large volumes of soil water back into the air through transpiration, and that moisture feeds cloud formation and rainfall over and downwind of the forest. Cut the forest and transpiration collapses, while the bare, lighter-coloured surface reflects more sunlight and heats differently.

The climate effect not offered here→Forests lock carbon in wood and in soil, so clearing and burning them releases carbon dioxide and adds to global warming.

Study next

The hydrological cycle: infiltration, percolation, runoff, evapotranspiration and groundwater rechargeSoil erosion and conservation — contour bunding, terracing, shelter belts, afforestationIndia's forest policy and law: the Forest (Conservation) Act 1980, the National Forest Policy 1988 and its one-third forest cover goal, and the Forest Survey of India's biennial reportJoint Forest Management and community forestry, and the Chipko movementDesertification, land degradation and the UN Convention to Combat DesertificationCarbon sinks, REDD+ and the role of forests in climate agreements

Common traps

Missing the emphasised 'not' and picking a true consequence such as soil erosion.
Reasoning that fewer trees means less water used and therefore more groundwater. Recharge, not tree consumption, sets the water table.
Assuming rainfall is purely a large-scale climatic matter that local land cover cannot touch. Transpiration recycling is a real and examined mechanism.
Confusing more surface runoff and more flooding with more groundwater. Water that runs off is precisely the water that does not recharge.
Treating biodiversity loss as caused by hunting alone. Habitat destruction and fragmentation are the larger cause.

Environment and ecology appear on EO/AO papers as short single-fact or direction-of-change items rather than as data or case studies. Deforestation, soil erosion, the water cycle, greenhouse gases and named conservation programmes are the recurring corners. The commonest shape is exactly this one — a list of effects with one sign reversed — and the second commonest is a cause-and-effect pairing item.

Related PYQs

No directly related past PYQ was found.

Practice

practice — not a real PYQ
Which one of the following best explains why a forested catchment recharges groundwater better than a cleared one ?
- (a)Trees release water into the soil through their roots
- (b)Canopy, litter and root channels increase infiltration and slow surface runoff
- (c)Forest soil is impermeable and holds water at the surface
- (d)Trees reduce evaporation by lowering the air temperature to freezing
Answer(b) Canopy, litter and root channels increase infiltration and slow surface runoff
practice — not a real PYQ
Loss of the thin fertile topsoil layer of a hill slope after the removal of tree cover is chiefly the result of
- (a)salinisation
- (b)waterlogging
- (c)soil erosion
- (d)leaching of nitrogen into groundwater
Answer(c) soil erosion

Why