Which of the following trees is dangerous for environment ?

Question

UnlockIAS · Accepted Answer

Correct — A, Eucalyptus. The case against eucalyptus rests on four well-documented properties. First, it transpires very heavily and draws a great deal of water out of the soil — so reliably that it has been planted on purpose to lower water tables and reduce soil salination, an intervention that can destroy ecologically productive wetland. Second, it is allelopathic: it releases compounds that inhibit other plant species from growing near it, which is why the ground under a eucalyptus stand is characteristically bare. Third, eucalyptus oil is highly flammable, and at high enough temperatures the oil expands and quickens the spread of wildfire; the Oakland Hills firestorm of 1991 in California is the standard case. Fourth, outside its native Australia the tree competes with native plants and typically does not support native animals, so a eucalyptus plantation adds tree cover without adding habitat. Critics of large-scale eucalyptus planting in India have argued the same points against social-forestry monocultures — falling water tables and the displacement of food crops — which is the argument this question is drawing on.

Why the other options are wrong — (b) A cultivated food crop with no comparable charge against it, and strictly not a tree at all: the banana is a giant herbaceous plant whose apparent trunk is a pseudostem of tightly rolled leaf bases. It is a thirsty crop, but it is grown as a crop on farmland rather than planted at scale as forestry, and nothing about it depletes water tables or suppresses neighbouring vegetation the way eucalyptus does.  (c) Close to the opposite of the answer. Neem, Azadirachta indica, is the classic drought-hardy indigenous tree of the Indian plains, valued for shade, for its timber and above all for the bio-pesticidal compounds in its seed and leaf. It is planted precisely because it thrives on poor soils and little water and coexists with everything around it.  (d) Babool, Acacia nilotica, is a thorny leguminous tree long naturalised in India's dry tracts and used in afforesting degraded and saline land, as well as for gum, fodder and fuelwood. The name is the source of a genuine confusion worth clearing up: 'vilayati babool', Prosopis juliflora, is a DIFFERENT and introduced species that is widely criticised for forming dense thickets and reducing local biodiversity. Desi babool is not that tree, and it is not what this question is pointing at.

Concept: Eucalyptus is a genus of some hundreds of species native to Australia, brought into India and much of the tropical world for plantation forestry because it grows fast, grows straight and yields pulpwood and poles within a few years. Those same qualities carry ecological costs, and they are worth learning as mechanisms rather than as a slogan: heavy transpiration lowering the local water table; allelopathy suppressing the understorey; volatile, flammable oils raising fire risk; and monoculture stands that count as tree cover in statistics while offering almost nothing to native insects, birds and mammals. This is the general problem with exotic plantation species — Prosopis juliflora and Lantana camara are the other names that recur in Indian environmental writing — and it is the reason forest policy distinguishes between raising tree cover and restoring a forest ecosystem.

State PCS 2022 Q80 — Environment & Ecology PYQ with Answer

State PCS 2022 Q80 — Environment & Ecology PYQ with Answer