Ch 8Environmental Issues — Class 12 Botany, concept-first.

Having already covered the structure and function of ecosystems, the chapter turns to the environmental problems those ecosystems now face — at the local, national and international level.

The greenhouse effect is the natural process by which certain atmospheric gases — chiefly carbon dioxide, methane, nitrous oxide and synthetic chlorofluorocarbons — absorb outgoing infrared heat from…

Rising mean global temperature sets off a chain of physical effects rather than a single uniform change.

Each major greenhouse gas has both natural and human (anthropogenic) sources, and separating the two matters for deciding what mitigation can realistically target.

Because global warming is driven by a build-up of specific gases from specific activities, the mitigation strategies target those same points.

The stratosphere is the upper of the two atmospheric layers closest to Earth (the troposphere being the lower one), and it hosts what is called the 'good' ozone layer, distinct from the ground-level '…

Ozone depletion's consequences fall into three linked categories. For human health, more UV-B reaching the surface raises the incidence of cataracts, throat and lung irritation, aggravated asthma and…

Forestry, in the sense used across this section, is the deliberate management of tree cover to deliver both economic and environmental benefit rather than leaving forests purely as land to be extracte…

Agroforestry combines trees, crops and livestock deliberately on the same plot of land, with the explicit aim of managing the beneficial interactions between them rather than treating cropping and tre…

Social forestry extends tree cultivation onto land outside formally designated forests, managed sustainably by local communities, with goals spanning carbon sequestration, climate-change mitigation, d…

Tamil Nadu's forestry extension centres run a defined set of activities to spread tree-growing outside formal forest land: training farmers and villagers in tree-growing methods; publicity and outreac…

Deforestation is the conversion of land that carried forest cover into land that no longer does — a permanent land-use change rather than temporary tree removal that regrows.

Afforestation is the reverse land-use change to deforestation: planting trees on land that carried no previous tree cover, converting non-forested land into forest by establishing suitable species.

Agrochemicals are the chemical inputs used to manage farming and livestock — fertilisers, liming and acidifying agents, soil conditioners, pesticides, and animal-husbandry chemicals such as antibiotic…

An invasive alien species is one that is not native to the ecosystem or country it is found in, spreads on its own once introduced, interferes with native species' biology and survival, threatens the…

Conservation is the deliberate set of management strategies used to protect India's biodiversity — germplasm conservation, in-situ methods, ex-situ methods and in-vitro methods — applied because the c…

The International Union for Conservation of Nature (IUCN), founded in 1948 and headquartered in Gland, Switzerland, is the world's oldest environmental organisation, functioning as a neutral forum bri…

A species is termed endemic when it is found restricted to one specific geographic region and nowhere else — the scale of that region can range from an entire continent down to a single island — and e…

Carbon Capture and Storage (CCS) is an engineered technology for pulling CO2 out of large point-source emitters — chiefly industrial plants and power stations — and storing it away from the atmosphere…

Rainwater harvesting (RWH) is the deliberate, on-site accumulation and storage of rainwater for later reuse, rather than allowing it to simply run off and be lost.

The environmental case for rainwater harvesting rests on a cluster of linked benefits. It promotes groundwater adequacy by actively recharging the water table rather than letting rainfall run off unus…

Beyond rainwater harvesting structures, natural and man-made water bodies such as lakes and ponds deliver environmental benefits that also translate into direct economic and public-health value: they…

Sewage disposal covers two related waste streams. Sewage — the faeces- and waste-water-laden effluent flowing from homes and factories through sewer systems — cannot be released directly into rivers a…

Environmental Impact Assessment (EIA) is an environmental-management tool used to forecast the environmental, socio-economic, cultural and human-health consequences of a proposed development project —…

Biodiversity Impact Assessment (BIA) is a decision-support tool that folds biodiversity considerations explicitly into development planning and implementation, ensuring development proposals are legal…

A Geographic Information System (GIS) is a computer system built to capture, store, check, manipulate, analyse, manage and display data tied to specific positions on Earth's surface, letting spatial o…

This closing Evaluation exercise reviews the chapter's full span of environmental-issue topics — greenhouse gases and ozone depletion, forestry and deforestation/afforestation, agrochemicals and invas…

Sample papers and previous-year board questions for this subject.