Impact of climate change
 on water resources, Agriculture, Forests, Land-use and Land-cover

 

 

 

Climate change is already having a significant impact on ecosystems, economies and communities. Rising average temperatures as a result of current climate change do not simply mean milder winters. As a result of climate change some regions will experience more extreme heat while others may cool slightly. Flooding, drought and intense summer heat could result. Violent storms and other extreme weather events could also result from the increased energy stored in our warming atmosphere.

One of the most serious impacts of climate change is the way it will affect water resources around the world. Water is intimately tied to other resource and social issues such as food supply, health, industry, transportation and ecosystem integrity.

The impacts of climate change are already being observed across the world.  Forests are expected to be among the most vulnerable in the world to climate change. These forests support countless species and ecosystems and are among the many examples of at-risk habitats. The global meltdown of ice sheets and alpine glaciers represents another, taking an immense toll on Arctic ecosystems.

Climate change also threatens the health of human beings through increased disease, freshwater shortages, worsened smog and more. These impacts also pose incalculable economic risks that far outweigh the economic risks of taking action today.

The world's leading scientists report that to prevent dangerous levels of global warming governments should act to limit global warming to less than 2ºC by taking concerted action to reduce greenhouse gas emissions.  The sooner we act to reduce greenhouse gases, the less severe the impacts will be.

Water Resources

Freshwater resources that humans rely on are highly sensitive to variations in weather and climate. In 2007, the Intergovernmental Panel on Climate Change (IPCC) reported with high confidence that climate change has a net negative impact on water resources and freshwater ecosystems in all regions.  The IPCC also found with very high confidence that arid and semi-arid areas are particularly exposed to freshwater impacts.

As the climate warms, it changes the nature of global rainfall, evaporation, snow, stream flow and other factors that affect water supply and quality. Specific impacts include:

·        Warmer water temperatures affect water quality and accelerate water pollution.

·        Sea level rise is projected to increase salt-water intrusion into groundwater in some regions. This reduces the amount of freshwater available for drinking and farming.

·        In some areas, shrinking glaciers and snow deposits threaten the water supply. Areas that depend on melted water runoff will likely see that runoff depleted, with less flow in the late summer and spring peaks occurring earlier. This can affect the ability to irrigate crops. (This situation is particularly acute for irrigation in South America, for irrigation and drinking supplies in central Asia, and for hydropower in Norway, the Alps, and the Pacific Northwest of North America.)

·        Increased extreme weather means more water falls on hardened ground unable to absorb it, leading to flash floods instead of a replenishment of soil moisture or groundwater levels.

·        Increased evaporation will reduce the effectiveness of reservoirs.

·        At the same time, human demand for water will grow for the purposes of cooling and hydration.

Freshwater environments around the world are already under excessive pressure from drainage, dredging, damming, pollution, extraction, silting and invasive species. 

Climate change - combined with other stresses - makes impacts worse, and also causes new threats. This is often a result of changing rainfall and evaporation patterns. Extremes of drought and flooding will become more common, causing displacement and conflict.

Melting glaciers: In mountainous regions, melting glaciers are impacting on freshwater ecosystems. Himalayan glaciers – giant rivers of ice that contain the largest stores of fresh water outside of the polar regions – feed great Asian rivers such as the Yangtze, Yellow, Ganges, Mekong and Indus. Over a billion people rely on these glaciers for drinking water, sanitation, agriculture and hydroelectric power.

Flooding and water shortages: Widespread floods, as the glaciers melt, will be followed by long-term water shortages, and massive humanitarian, social and environmental problems in western China, Nepal and northern India. Less fresh water means less agriculture, food and income.

Wildlife affected: The Ganges river dolphin – which lives in the river systems of Nepal, India and Bangladesh – is very vulnerable to changes in its limited habitat. Increases in water temperatures may dramatically affect fish populations that are the dolphins’ food source.  The river-dwelling gharial – a critically endangered crocodile-like reptile found mostly in India and Nepal – is under threat from the growing number of irrigation schemes being developed along rivers in the wake of increased drought conditions.

Agriculture

Solar radiation, temperature, and precipitation are the main drivers of crop growth; therefore agriculture has always been highly dependent on climate patterns and variations.  Climate change is projected to have significant impacts on agricultural conditions, food supply, and food security.

Overall, climate change could result in a variety of impacts on agriculture. Some of these effects are biophysical, some are ecological, and some are economic, including:

·        A shift in climate and agricultural zones towards the poles

·        Changes in production patterns due to higher temperatures

·      A boost in agricultural productivity due to increased carbon dioxide in the atmosphere

·        Changing precipitation patterns

·        Increased vulnerability of the landless and the poor

However, agriculture is itself responsible for an estimated one third of climate change. It is generally agreed that about 25% of carbon dioxide emissions, are produced by agricultural sources, mainly deforestation, the use of fossil fuel-based fertilizers, and the burning of biomass. Most of the methane in the atmosphere comes from domestic ruminants, forest fires, wetland rice cultivation and waste products, while conventional tillage and fertilizer use account for 70% of the nitrous oxides. According to the Intergovernmental Panel on Climate Change, the three main causes of the increase in greenhouse gases observed over the past 250 years have been fossil fuels, land use, and agriculture.

Over the past centuries, human ingenuity has led to technological advances in agriculture that have allowed substantial increase in crop yields, in part stimulated to meet population growth. Intensive agricultural methods are reported to have detrimental effects on the environment.

The agricultural sector has become one of the main driving forces in gas emissions and land use effects. For example, agriculture contributes to greenhouse gas increases through land use in different ways:

·      CO2 emissions linked to deforestation in temperate regions: where forests and woodlands are cleared to make room for fields and pastures.

·        Methane emissions from rice cultivation and enteric fermentation in cattle

·        Nitrous oxide emissions from fertilizer applications

Together, these agricultural processes comprise 54% of methane emissions, roughly 80% of nitrous oxide emissions, and virtually all carbon dioxide emissions tied to land use. Deforestation for land cleaning purposes also affects regional carbon reuptake, which can result in increased concentrations of CO2, the dominant greenhouse gas. Worldwide, livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the Earth.

Forests

Most people know how vital forests are – they soak up carbon dioxide, the main greenhouse gas responsible for global warming, and help regulate the world’s climate. They’re also home to countless plant and animal species. Communities, local governments and businesses need to ensure the world’s forests are protected.

Sub-Arctic boreal forests: Impacts vary in different kinds of forests. Sub-Arctic boreal forests are likely to be particularly badly affected, with tree lines gradually retreating north as temperatures rise.

Temperate forests: In tropical forests such as the Amazon, where there’s abundant biodiversity, even modest levels of climate change can cause high levels of extinction. Another complication is that tropical forests are often in countries where there’s less access to information, technology and financial resources.

Impacts of deforestation: When large areas of forest are destroyed – whether razed for commercial reasons or dried by a warming climate – it iss disastrous for the local species and communities that rely on them. It is also bad for all life on Earth. Dying trees emit their stores of carbon dioxide, adding to atmospheric greenhouse gases and setting us on a course for runaway global warming.  Forest and vegetation loss can also cause soil erosion, landslides in mountainous areas and loss of agricultural land.

Forests are more prone to deadly infestations Milder winters and longer summers allow tree-killing insects to thrive. Meanwhile, trees weakened by prolonged drought have lower defense mechanisms. This cycle of warmer weather, weak trees and thriving insects is likely the culprit behind the massive die-off of 70,000 square miles of Rocky Mountain conifers.

Land Use – Land Cover

Future patterns of land use and land cover will interact with climate changes to affect human communities and ecosystems. At the same time, future climate changes will also affect how and where humans live and use land for various purposes. Studies suggest that the general historical trends of land-use and land-cover changes will continue, with some important regional differences. These projections all assume continued population growth based on assumed or statistically modeled rates of birth, death, and migration, which will result in changes in land use and land cover that are spread unevenly across the globe.

The conversion of land-use to provide food and shelter in response to climate change is one of the major modes of human adaptation to the global environment, as well as changes in the local environment, such as the hydrological processes at the watershed scale. Meanwhile, the impact of global climate change is mediated at regional and local scales by biophysical processes associated with land-use and land-cover (LULC). For instance, changes in the global climate have a significant impact on local and regional hydrological regimes and processes, which in turn affect ecological, social and economical systems. It is clear that both climate change and land-use change are important drivers of changes in a watershed’s hydrology; however, their relative effects are difficult to separate empirically, especially in watershed land-use planning and management. Moreover, the effects of climate change on land-use should be considered from two perspectives:

1.     How land-use might be altered by climate change; and

2.     What land management strategies would mitigate the negative effects of climate change.

Therefore, adapting land-use patterns is an essential aspect of strategies designed to minimize the negative outcomes of the now-unavoidable climate change at regional and local scales, including adapting watershed land-use patterns to accommodate the impact of climate change on a region’s hydrology.

The impacts of climate change on environmental systems, such as hydrological processes, are gradually and cumulatively spreading from the global scale to local scales. Actions associated with building adaptive capacity may include communicating information about climate change, building awareness of the potential impacts of such change, maintaining the well-being of residents, protecting property/land, maintaining economic growth, and exploiting new opportunities. Increasing the ability of environmental systems to adapt, or strengthening their adaptive capacity, is already an important consideration in responding to climatic changes. Therefore, adaptation strategies and decisions are more likely to focus on reducing the cumulative impacts of climate change, and ensuring that the distributional impacts of adaptation are minimized. In national, regional and local land-use planning, the impact of global climate change is mediated at regional and local scales by biophysical processes associated with land-use and land-cover (LULC), such as the hydrological processes associated with land-use and land-cover. For example, the impact of climate change on water availability and quality will probably threaten the sustainability of water uses and increase the risk of lacking water for social and ecological systems. Moreover, land-use is a key factor that must be considered when predicting potential future hydrological responses of a watershed, and then can be adapted to minimize the impacts of climate change on hydrological processes. Assessing the effects of land-use on a region’s hydrology is of special interest when discussing the expected effects of climate change. Some recent studies assessed how land-use patterns and climate change singly and jointly affect a region’s hydrology. 

 REFERENCES:

Land Use and Land Cover Change:

http://nca2014.globalchange.gov/report/sectors/land-use-and-land-cover-change

Notes & Handouts

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Kumaon Himalayas

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