Impact of Climate Change

Agriculture and Food Security

Climate change alters the physical factors that determine agricultural productivity - temperature, precipitation, solar radiation, atmospheric carbon dioxide concentration, and the frequency and intensity of extreme events. These changes affect water availability for irrigation, plant physiology, pest and disease incidence, soil health and the seasonal calendar for cropping. Together they influence both the quantity and quality of agricultural output and hence food security.

• Changes in temperature and precipitation affect crop growth, yield, cropping season length and the suitability of areas for particular crops.
• Rising greenhouse gas concentrations have regionally variable effects: moderate warming (about 1-3°C rise in mean temperature) may benefit yields in some temperate regions, while in lower latitudes and seasonally dry tropics even moderate increases (1-2°C) are likely to reduce yields of major cereals. Warming beyond 3°C is expected to reduce production across most regions.
• Climate change interacts with pests, diseases and weeds; altered climates can increase the range, life-cycle speed and outbreak frequency of many agricultural pests and pathogens.
• The IPCC Third Assessment Report (2001) concluded that climate change would disproportionately affect the poorest countries and reduce agricultural productivity in many low-latitude regions, mainly through reduced water availability and increased pest incidence.
• Studies indicate that in South Asia losses of regional staples such as rice, millet and maize could exceed 10 per cent by 2030 under projected climate changes.
• Thawing of snow and permafrost may expand arable land in some high-latitude regions by reducing frozen ground, while sea-level rise and coastal erosion will reduce arable land along many shorelines.
• Coastal inundation, salinisation of soils and groundwater, and more frequent extreme events increase the risk of land degradation and decline in productive area.
• The International Commission for Snow and Ice (ICSE) reported rapid shrinkage of Himalayan glaciers and warned that, if trends continued, some glaciers could disappear by 2035, threatening dry-season river flows on which large agricultural areas depend.
• Reduced agricultural production in low-income countries would magnify risks to rural livelihoods and increase vulnerability to food insecurity.

(i) Impacts on Indian agriculture

India's agriculture is especially vulnerable because a large share of cultivated area is rain-fed and the cropping system is tightly linked to the monsoon. Climate-induced changes in rainfall distribution, monsoon onset and retreat, and temperature will therefore have strong consequences for national food security and the rural economy.

• A substantial portion of India's arable land is rain-fed, so agricultural productivity is highly sensitive to both the amount and timing of rainfall.
• Shifts in overall rainfall and its intra-seasonal distribution pose serious threats to cropping decisions, sowing and harvesting windows, and yields.
• Summer (southwest) monsoon rainfall provides nearly 70% of India's annual precipitation and is central to agricultural performance; several studies indicate possible declines in summer rainfall by the 2050s under some scenarios.
• Semi-arid western India is projected to see higher than normal rainfall in some simulations as temperatures rise, while parts of central India could experience a 10-20% decline in winter rainfall by the 2050s.
• Small changes in climate can create large problems for water resources in arid and semi-arid regions such as northwest India, amplifying drought risk and reducing irrigation reliability.
• Increased temperatures and lower water availability are likely to reduce yields for many crops across the Indo-Gangetic Plains, and may disproportionately reduce rabi (winter) season productivity relative to kharif (monsoon) crops.
• Higher temperatures increase crop nutrient demand; this can raise fertiliser requirements, add to farmers' costs and increase greenhouse gas and ammonia emissions.
• Greater frequency of droughts, floods, storms and cyclones will increase production variability, raising risks for farmers and food markets.

Adaptation and mitigation in agriculture

• Adopt climate-resilient crop varieties (drought-, heat- and flood-tolerant) and adjust cropping calendars to shifted monsoon patterns.
• Improve water-use efficiency through micro-irrigation (drip and sprinkler systems), conjunctive use of surface and groundwater, and water-harvesting structures.
• Promote soil health (organic matter, conservation tillage), integrated pest management and diversified cropping systems to reduce vulnerability.
• Strengthen agricultural extension, weather advisory services and crop insurance schemes to assist farmers in anticipatory decision-making.
• Reduce agriculture's contribution to greenhouse gases through improved fertiliser management, reduced residue burning and enhanced livestock practices.

Water Stress and Water Insecurity

Water security depends on reliable quantity and quality of freshwater for drinking, agriculture, industry and ecosystems. Climate change alters the hydrological cycle - precipitation patterns, evapotranspiration, snow and glacier melt, and the frequency of intense rainfall - and thereby exacerbates existing stresses on water resources.

• Climate change is expected to exacerbate current stresses on water resources through altered timing and magnitude of runoff and more frequent extremes.
• Between 75 and 250 million people were projected to be exposed to increased water stress by 2020 as a consequence of climate change.
• Growing population and rising per-capita water use increase pressure on limited freshwater supplies, intensifying competition for water within and between sectors and countries.
• Warming has reduced mountain glaciers and snow cover in both hemispheres and this decline is projected to accelerate during the 21st century, reducing dry-season flows in basins fed by glacier melt.
• By the 2050s, freshwater availability in Central, South, East and South-East Asia - particularly in large river basins - is projected to decrease under many scenarios.
• A warmer climate accelerates the hydrological cycle, altering rainfall intensity and timing: many regions may see more heavy rainfall events even as mean rainfall declines.
• Frequency of severe floods in large river basins rose during the 20th century; increasing floods challenge infrastructure, public health and water quality.
• Rising temperatures affect the physical, chemical and biological properties of lakes and rivers, often harming freshwater species and degrading water quality.
• In coastal areas, sea-level rise increases salinisation of groundwater and reduces the availability of freshwater in coastal aquifers.

(i) Impacts on water situation in India

India faces mounting water stress because of population growth, economic development, and climate-driven changes to both surface and groundwater supplies. Himalayan glacier retreat, changes in monsoon patterns and increased frequency of extreme events are major concerns for Indian water security.

• The Himalayan glaciers feed perennial rivers such as the Indus, Ganga and Brahmaputra; changes in glacier mass and snow cover will alter seasonal river flows.
• Land-use changes (deforestation, agriculture expansion and urbanisation) in the Himalayan region have increased hydrological disasters, sedimentation and pollution of lakes and rivers.
• Evidence indicates significant retreat of some Himalayan glaciers since the 19th century; records suggest the Gangotri glacier is retreating by about 28 m per year in recent decades.
• Accelerated glacial melt may raise summer flows for several decades but will be followed by reduced flows as glaciers shrink, threatening dry-season irrigation and hydropower.
• Observed changes in rainfall patterns across the 20th century have already affected river behaviour in the Indo-Gangetic Plain, with some rivers changing course multiple times, increasing flood risk (for example, the recent Kosi floods in Nepal and Bihar).
• Estimates suggested India would need to increase food production substantially by 2020 (to about 300 million tonnes of foodgrain and a roughly 50% increase in total production) to feed a projected population of about 1.30 billion, intensifying water demand for agriculture.
• Rising population and demand will accelerate groundwater withdrawal, reducing groundwater recharge and threatening long-term sustainability: groundwater overexploitation has led to falling water tables in many regions.
• Currently, agriculture consumes the largest share of water in India - about 83% of available water - and even with efficiency improvements it may remain the dominant user (possibly around 68% by 2050).
• Augmentation of supply, conservation of existing resources and improved efficiency across sectors will be needed to meet rising demand.
• Developing countries such as India are likely to experience more severe consequences because their economies are more dependent on climate-sensitive sectors and already face resource stresses.

Adaptation and water management responses

• Integrated watershed management, rainwater harvesting, recharge of aquifers and sustainable groundwater governance to arrest overexploitation.
• Improved irrigation efficiency (micro-irrigation), crop diversification and scheduling to reduce agricultural water demand.
• Floodplain restoration, improved river basin planning and flood management infrastructure to reduce flood damage and sedimentation.
• Climate-informed water allocation policies, conjunctive use of surface and groundwater and transboundary cooperation in shared basins.

Rise in Sea Levels

Sea-level rise results from two primary processes: thermal expansion of warming ocean water and addition of water from melting land ice (glaciers and ice sheets). Satellite altimetry and tide-gauge records show that global mean sea level rose faster since the early 1990s than during the previous half-century.

• Since 1993, satellite observations indicate a rate of sea-level rise significantly higher than the long-term average for the 20th century.
• The IPCC warns that ice-sheet disintegration could accelerate sea-level rise, with major implications for coastal populations and infrastructure.
• A global warming of about 3-4°C could expose an estimated 330 million people to permanent or temporary displacement from coastal flooding.
• Warming seas also increase the potential intensity of tropical storms and cyclones, worsening storm surge and coastal flooding impacts.

(i) Impacts on coastal states in India

• Coastal states such as Maharashtra, Goa and Gujarat face risks from inundation, coastal erosion and damage to infrastructure and agricultural land.
• Goa is particularly vulnerable given its low-lying coastal plains and tourism infrastructure; significant land loss and beach erosion could occur.
• Low-lying areas and tidal flats, for example in parts of Mumbai (northern suburbs and creeks), are vulnerable to land loss and increased flooding.
• Coastal flooding and salinisation reduce freshwater availability, increasing water scarcity for communities and agriculture.
• States such as Odisha (Orissa) could face more intense cyclones and storm surges.
• Coastal ecosystems - mangroves, coral reefs, seagrass beds - are threatened by rising sea levels, higher sea temperatures and changing salinity; loss of these ecosystems reduces natural coastal protection and fisheries productivity.
• Populations in the Ganges Delta face compounded flood risks from sea-level rise and riverine flooding, threatening densely populated lowlands.

Coastal adaptation measures

• Conserve and restore natural buffers such as mangroves and coral reefs to provide coastal protection and sustain fisheries.
• Land-use planning that avoids development in high-risk coastal zones and includes managed retreat where necessary.
• Strengthen coastal infrastructure resilience and develop early warning and evacuation systems for storm surges and extreme events.

Ecosystems and Biodiversity

Climate change threatens biodiversity both directly (through changes in temperature, precipitation and sea level) and indirectly (through altered disturbance regimes, invasive species and habitat fragmentation). Loss of species and ecosystem services undermines livelihoods, food security and resilience.

• Climate change can drive local extinctions when species cannot shift their ranges or adapt fast enough to new conditions.
• The projected loss of species and ecosystems in many regions will be largely driven by human-induced climate changes combined with land-use change and other pressures.
• The World Wide Fund for Nature (WWF) and other conservation bodies have highlighted that natural areas from the tropics to the poles are at risk and that some of the world's most vulnerable natural areas may face catastrophic loss of species.
• Marine ecosystems face particular threats from rising sea temperatures, changing ocean circulation and ocean acidification as dissolved carbon dioxide increases, affecting shell-forming organisms, corals and their dependent food webs.
• Coral bleaching, driven by higher sea temperatures, is a clear and visible consequence that reduces reef cover and fish habitats.

Impacts on India's biodiversity

India's wide range of ecosystems - from glaciers and high mountains to deserts, coasts and tropical forests - makes it a global biodiversity hotspot. Climate change threatens these ecosystems in multiple ways.

• Mountain ecosystems are biodiversity hotspots but particularly vulnerable to warming and human disturbance; increased fragmentation and loss of habitat are already being observed.
• The Himalayan ecosystem is critical for perennial rivers and supports unique flora and fauna; glacier retreat, altered snowmelt and higher temperatures increase risks of Glacial Lake Outburst Floods (GLOFs), causing catastrophic downstream flooding and damage to life and infrastructure.
• Himalayan river systems are tied to the Indo-Gangetic Plain, a major agricultural region that supports a large share of India's rural population.
• The Indian desert (arid and semi-arid regions) covers about 127.3 million hectares (38.8%) of the country and supports diverse fauna and migratory birds; there is evidence of desert expansion and episodes of unusual flooding, indicating altered climatic patterns.
• Coastal and marine ecosystems, including mangroves, act as carbon sinks and natural barriers to storms and flooding; their loss reduces coastal resilience and threatens fisheries and livelihoods.
• Coral bleaching and marine ecosystem changes have direct consequences for coastal communities dependent on fisheries and tourism.
• Peninsular river systems remain monsoon dependent; changes in monsoon behaviour therefore affect peninsular ecosystems and water availability for agriculture and communities.
• Overall, India's rich biodiversity and ecosystem services are highly dependent on stable climatic and hydrological regimes; climate change compounds existing pressures from land-use change, pollution and resource extraction.

Conservation and adaptation strategies for biodiversity

• Protect and connect habitats through networks of protected areas and ecological corridors to facilitate species migration and adaptation.
• Restore degraded ecosystems (mangroves, wetlands, forests) to enhance carbon sequestration and ecosystem resilience.
• Integrate climate risks into conservation planning, including monitoring, assisted migration where appropriate and ex-situ conservation for at-risk species.
• Promote community-based natural resource management that combines biodiversity conservation with local livelihoods.

Climate Change and Health

Climate change poses multiple direct and indirect threats to human health. These arise from higher average temperatures, more frequent and intense heatwaves, altered patterns of infectious disease, compromised water and food supplies, and damages to health infrastructure from extreme events.

• Annual global mortality and morbidity burdens attributable to environmental and public-health determinants are substantial: about 800,000 deaths linked to air pollution, 1.8 million deaths from diarrhoeal disease associated with unsafe water, sanitation and hygiene, 3.5 million deaths from undernutrition and approximately 60,000 deaths from natural disasters are estimated in combined global assessments.
• Higher and more variable temperatures worsen air quality (e.g., by increasing ground-level ozone and particulate formation) and increase respiratory and cardiovascular disease burdens.
• Changes in precipitation and flooding increase the risk of water contamination, raising rates of diarrhoeal diseases and water-borne infections.
• Floods create breeding sites for vectors such as mosquitoes, increasing risks of vector-borne diseases; droughts and resultant migration and overcrowding can also promote disease transmission.
• Evidence indicates expansion of vector ranges: malaria has been reported in higher elevations in countries such as Nepal and Bhutan; models suggest an additional 220-400 million people could be exposed to malaria under some scenarios, and the global population at risk of dengue may increase by up to 2 billion by the 2080s.
• Reduced crop yields and food insecurity due to climate impacts increase risks of malnutrition, especially among vulnerable populations.
• Stratospheric ozone depletion - largely caused historically by chlorofluorocarbons and other halogenated compounds - increases surface ultraviolet radiation and raises risks of skin cancers and cataracts; this issue is related to but distinct from greenhouse-gas driven warming.
• Health impacts from climate change are often greatest among the poorest populations who have limited access to healthcare, sanitation and resilient livelihoods, thereby widening health inequalities.

Health adaptation and preparedness

• Strengthen public health systems, disease surveillance and early-warning systems for heatwaves, floods and disease outbreaks.
• Improve access to safe water, sanitation and hygiene (WASH) and invest in resilient water and sanitation infrastructure.
• Implement vector control programmes, community health education and vaccination where applicable to reduce infectious disease burdens.
• Develop heat-health action plans, expand cooling centres and protect vulnerable populations from heat stress.
• Integrate climate risk assessments into health planning and infrastructure design to maintain service delivery during extreme events.

Summary

Climate change affects multiple interdependent systems - agriculture, water, coasts, ecosystems and human health - with regionally varied outcomes. India, with its dependence on monsoon rains, large rain-fed agricultural area, extensive coastline and rich biodiversity, faces distinct vulnerabilities including reduced crop yields, increasing water stress, glacier retreat, sea-level rise, ecosystem degradation and expanded health risks. Effective response requires integrated adaptation measures (water and soil conservation, resilient agriculture, ecosystem restoration, public-health preparedness), policy reforms, technological adoption and international cooperation to reduce emissions and build resilience.