The relationship between humans and the environment is highly complex. Understanding these complexities is essential for analyzing contemporary environmental problems. It is only through this comprehension that effective solutions can be devised.
Upon examining the root causes of most major environmental challenges, it becomes clear that anthropogenic factors are largely responsible. Economic activities, especially industrialisation and a consumerist lifestyle, have significantly increased our carbon footprint and ecological footprint, thereby disrupting the natural life-support systems.
To simplify, carbon footprint and ecological footprint represent the environmental load that humans impose on the global ecosystem.
As discussed in earlier units, the environment is a system of dynamic interrelationships between biotic and abiotic components. These relationships are maintained through various natural cycles, such as the hydrological cycle, sedimentary cycle, and gaseous cycle. Among living organisms, systems like the food chain and food web maintain ecological balance.
These cycles function in a state of equilibrium in an undisturbed natural environment, forming the foundation for life on Earth. Humans must act in accordance with this balance. However, excessive human interference has disrupted these cycles, endangering natural balance and long-term sustainability.
Many environmental issues are trans-boundary, meaning they extend beyond the geographical boundaries of any single nation. Examples include air pollution, water pollution, and acid rain, all of which can impact neighboring countries.
The irony lies in the fact that those most affected by such issues are often not the ones responsible for causing them. This raises questions of environmental justice and equity that remain unresolved.
Major environmental problems are now global or regional in nature. Therefore, it is imperative that individuals, communities, and societies act consciously to mitigate these issues. Such proactive efforts are crucial for safeguarding human well-being and supporting socio-economic development.
Environmental problems have emerged due to the complex and dynamic interplay of socio-economic, technological, and institutional factors. The previous section on the nature of environmental issues has provided insight into these causative factors. Can you identify some of these factors?
Key contributing factors include rapid industrialization, urbanization, population growth, intensification of agriculture, and increased reliance on fossil fuel-based energy and transportation. Underlying factors such as poverty, inequity, and inequality also play a significant role.
Industrialization is considered one of the major causative factors of today's environmental issues. During the post-Renaissance period, mechanization and industrialization were seen as a boon for human progress. However, the detrimental effects of industrialization on both human life and Earth's sustainability were not foreseen.
The release of greenhouse gases and the discharge of solid and liquid wastes from industries have led to various environmental challenges, including pollution, global warming, acid rain, and ozone layer depletion.
Fossil fuel use is often considered a "necessary evil." This is because, despite the growing awareness of its harmful effects, fossil fuel consumption remains essential across multiple sectors, including agriculture, industry, transportation, and household energy. Its widespread use contributes to various forms of pollution and alters the composition of the atmosphere, especially in the lower atmosphere.
This alteration results in environmental problems such as global warming, acid rain, and ozone layer depletion.
The relationship between population and the environment is complex. It is not merely the number of people that affects the environment, but also the quality of life, including factors like living standards, consumption patterns, and technological access. While enhancing the quality of life is essential, it should not come at the expense of the environment.
As our exploitative use of environmental resources surpasses the threshold limits of natural support systems, there is a growing need to balance population growth, consumerist lifestyles, and the natural resources provided by the Earth. Sustainable development has emerged as the necessary framework to achieve this balance.
For highly populous countries like China and India, the urgency of this issue is even greater. India, with 17% of the global population, has only 2.4% of the world's land area. Projections suggest that by 2030, India will become the most populous country globally. Thus, there is an urgent need to revise developmental activities to be more eco-friendly and sustainable.
Urbanization, closely tied to industrialization, is typically considered a positive indicator of development. However, it has become a major environmental challenge. Urban areas, being hubs of industrialization and mechanization, are significant sources of greenhouse gas emissions, air pollution, water pollution, noise pollution, and waste generation.
In developing countries, lack of economic opportunities forces large numbers of people to migrate from rural areas to urban centers. This mass migration often leads to unplanned urban growth, which strains resources and infrastructural services like housing, transportation, water supply, sewerage, and energy.
Consequently, urban environments deteriorate, facing issues such as air and water quality deterioration, waste accumulation, proliferation of slums, and undesirable land-use changes.
The IPAT theory proposed by Ehrlich and Ehrlich provides insights into how consumption patterns affect the environment. In the equation, affluence refers to the average consumption per individual. Today's consumption patterns exhibit significant inequality between developed and developing countries, as well as between rich and poor within nations.
This disparity means that a large portion of the global population is deprived of access to basic resources like clean drinking water, fresh air, and balanced diets.
There is a pressing need for the equitable distribution of resources to ensure that everyone has the right to a decent standard of living.
You have likely been reading, hearing, and viewing discussions and debates related to the causes, effects, and remedial measures associated with global warming. In this section, we will explore these aspects in detail.
Global warming refers to the rise in atmospheric temperature and the consequent changes in radiation balance, primarily due to human actions. Recent estimates show that over the past 100 years, surface air temperatures have increased by about 0.5°C to 0.7°C.
In temperate regions, greenhouses are constructed to grow various types of flowers and vegetables. A greenhouse allows the Sun’s rays to enter but prevents them from exiting, keeping the interior warm. Similarly, in the context of Earth, the greenhouse effect refers to the process of warming the Earth's surface, particularly the lower atmosphere, by absorbing the Sun's rays and not allowing them to escape.
This effect is mainly caused by certain gases that function like the glass panels of a greenhouse. These gases include carbon dioxide (CO2), methane (CH4), nitrous oxides (NOx), and chlorofluorocarbons (CFCs), which are known as greenhouse gases. Deforestation and industrialization have exacerbated the accumulation of these gases in the atmosphere.
Among these gases, carbon dioxide contributes about 55%, CFCs contribute 24%, methane contributes 15%, and nitrous oxide contributes 6% to the heating of the atmosphere.
The following table summarizes the major greenhouse gases and their primary sources:
| Greenhouse Gases | Major Sources |
|---|---|
| Carbon Dioxide (CO2) | Burning of fossil fuels, firewood, automobiles, and factories |
| Methane (CH4) | Growing paddy fields, livestock, waste dumps, and coal mining |
| Aerosols | Coolants in refrigerators and air conditioning devices |
| Nitrous Oxide (NO2) | Emission from chemical industries, deforestation, and certain agricultural practices |
| Halocarbon (e.g., CFC-11, CFC-12) | Refrigeration agents and industrial processes |
Some of the major consequences of the greenhouse effect are:
To mitigate the consequences of global warming, some of the remedial measures include:
The depletion of the ozone layer is another major global environmental issue, similar to global warming. Before discussing this issue, let's first understand what ozone and the ozone layer are. You might have come across information about the ozone layer in your science and social science books, as well as in newspapers and magazines.
Not only is the ozone layer thinning, but in some places, it has temporarily disappeared. A hole in the ozone layer has developed over the Antarctic since 1979 and has persisted for an extended period. In 1988, an ozone hole was discovered over the Arctic, and it has continued to last longer each year since then.
In simpler terms, ozone is a form of oxygen consisting of three atoms (O3) rather than the more common two atoms (O2). It is formed in the upper atmosphere by the action of solar radiation on oxygen molecules.
About 90% of atmospheric ozone is located in the stratosphere, between 15 to 48 kilometers above the Earth's surface. Though ozone constitutes less than 0.002% of the volume of the atmosphere, its role is critical for life on Earth. The ozone layer strongly absorbs harmful ultraviolet radiation from the sun, acting as a protective shield.
Fig. 15.1 (a) shows various atmospheric zones, and (b) illustrates the location of the ozone layer.
The depletion of the ozone layer is primarily caused by human activities that release certain chemicals into the stratosphere, which consume ozone and reduce its concentration. Some of the main gases responsible for ozone depletion include:
These chemicals are primarily compounds of chlorine or bromine, which can reach the stratosphere and break down ozone molecules catalytically. Initially, scientists believed CFCs were harmless because they are odorless, non-flammable, non-corrosive, and non-toxic. This led to widespread use of CFCs in refrigeration, air conditioning, foam and plastic manufacturing, and aerosol sprays. Nitrogen oxides, released by supersonic jets flying at altitudes of 18–22 kilometers, also contribute to ozone depletion.
The depletion of the ozone layer has major harmful effects, which can be grouped into four categories:
Preventing further ozone layer depletion requires actions at both individual and governmental levels. Over the last two decades, global initiatives have been launched to address this issue. A significant step was the Montreal Protocol of 1987, signed on September 16, 1987, by the United Nations and 45 other countries. The protocol aims to protect the ozone layer by reducing the production of substances responsible for ozone depletion. India is also a signatory to this protocol.
Research is ongoing to develop substitutes for CFCs in refrigeration and air conditioning systems. The good news is that, due to concerted efforts, the ozone layer is slowly recovering. According to a United Nations report in November 2018, the ozone layer is healing over both hemispheres. The ozone layer above the northern hemisphere is expected to be fully healed by the 2030s, and the southern hemisphere by the 2050s.
Climate change is one of the major environmental problems of the 21st century. This issue has affected the life and livelihoods of millions of people across the globe. But before discussing the impacts of climate change, let's first understand what it means.
In simpler terms, climate change refers to any substantial change in the Earth's climate that lasts for an extended period of time. Typically, a minimum period of thirty to thirty-five years is considered for analyzing or predicting the climatic conditions of a region.
The two major elements of climate are temperature and precipitation. Let's explore one of the formal and widely accepted definitions of climate change. According to the Inter-Governmental Panel on Climate Change (IPCC), climate change refers to “any change in climate over time, whether due to natural variability or as a result of human activity” (IPCC, 2001a).
You might be wondering, climate change has occurred many times throughout the Earth's history. Why is there so much concern now? The difference today is that current climate change is primarily driven by human activities.
Evidence suggests that previous climate changes were due to natural processes. However, in this section, we will focus on climate change caused by anthropogenic activities that have escalated in recent times, particularly since the Industrial Revolution in the 17th century.
Did you know that the Earth would not be habitable without the presence of some naturally occurring greenhouse gases (GHGs)? These gases trap heat in the atmosphere, making Earth warm enough for life to thrive. Without the greenhouse effect, the Earth's average temperature would be around -17°C, which would be unsuitable for the growth of biota.
Natural greenhouse gases are beneficial in their natural amounts, but the problem arises when human activities release excessive amounts of these gases, particularly since industrialization began.
Climate scientists have been gathering evidence on key parameters of climate change for over a century. This data is collected from a variety of sources, including numerous weather stations, satellites, ships, aircraft, weather balloons, and buoys. Over the past three to four decades, detailed data has been gathered to track changes in the climate.
At the international level, these data and findings are compiled and analyzed to identify global trends, which are reported by the Intergovernmental Panel on Climate Change (IPCC) in the form of Assessment Reports. As of now, the IPCC has published five such reports. For more details about IPCC and its reports, you can visit its website: http://www.ipcc.ch.
Some of the key indicators used to assess the warming of the climate are:
Meteorologists have been analyzing temperature data available since 1880. It has been observed that the years with the warmest land-surface temperatures were 2005 and 2010 in the Northern Hemisphere and 2009 in the Southern Hemisphere. It has also been observed that the period from 2000 to 2010 was the warmest decade since 1880. The data from long-term climate reconstructions of temperature point to the present time as the warmest in the last 120,000 years. These reconstructions also suggest that the increase in temperature during the twentieth century is extremely likely (within a confidence interval of greater than 95%–100%) the largest to occur in any century over the past 1000 years.
According to the National Oceanic and Atmospheric Administration (NOAA), ocean temperatures have also been rising. According to NOAA, sea surface temperatures increased at an average rate of 0.07°C (0.13°F) per year from 1901 to 2012 as oceans absorbed atmospheric heat. This rise is reflected in measurements of upper-ocean heat content, which includes the upper 700m (2296 ft.) of ocean.
As discussed in the previous paragraph, there has been an increase in surface temperature both at land and sea. This rise in temperature has a direct relationship with the melting of glacial and sea ice. As temperatures rise in Earth's atmosphere, glaciers are losing ice mass, shrinking in size. This process is known as glacial retreat.
Earth's two largest ice sheets, Greenland and Antarctica, are also losing ice mass. This is evident from satellite records. Analysis of satellite data of July 2012 revealed that 97% of the ice sheet’s surface was melting. This was the greatest extent in the 30-year record of satellite measurements. Another analysis related to summer melt of the Greenland ice sheet showed a 30% increase from 1979 to 2006. Scientists now estimate that between one- and two-thirds of Arctic permafrost will thaw over the next 200 years.
Similar observations have also been noticed in relation to sea ice. The maximum sea ice cover in the world is found in the Arctic Sea. The extent of Arctic Sea ice varies over the course of a year. Every summer, some amount of sea ice thaws, whereas in winter, the ice refreezes. Satellite data has revealed that the minimum extent of summer sea-ice occurs in September, while maximum extent of winter sea-ice occurs in February or early March. However, since 1979, this has declined. September sea ice is declining at a rate of 11% per decade in comparison to the 1979–2000 average and reached its lowest extent in 2012. The accelerating decline of summer sea ice, in association with record losses of sea ice in 2007 and 2012, suggests that summer sea ice may disappear sooner than predicted by most models. Some scientists have also estimated an ice-free summer Arctic Ocean within the next few decades.
Sea level is rising more quickly than the predictions simulated by most climate models. During the last century, sea level rose 17–21 cm (6.7–8.3 in.). However, this rise is not uniform across the globe. A greater rise has been observed in some areas like the Atlantic coast of the U.S. than at any time during the past 2000 years.
Scientists use tidal gauges and satellites to assess the rise in sea level. Tidal gauge records from 1901 to 2010 show that sea level rose at a rate of 1.7 mm (0.07 in.) per year. Satellite data for the period 1993 - 2013 show that sea level rose 3.16 mm (0.12 in.) per year. This rise is primarily due to two major factors: about two-thirds of the rise comes from the melting of glaciers and ice sheets, while the rest comes from the thermal expansion of seawater due to the absorption of atmospheric heat.
Global average specific humidity has increased by about 0.1 g of water vapor per kilogram of air per decade since 1973. This change is consistent with rising air temperatures. As a result, warm air has a greater capacity to absorb water vapor. The greater amount of water vapor in the atmosphere affects weather patterns, leading to extreme events like heatwaves, increased precipitation, and floods. According to the World Meteorological Organization, the decade from 2001 to 2010 showed evidence of a worldwide increase in extreme events.
However, to establish a strong linkage between trends related to extreme weather and climate change requires data for a longer timeframe than what is currently available.
Each of the last three decades has been successively warmer on Earth’s surface than any preceding decade since 1850.
Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010.
The Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink, and Arctic sea ice and northern Hemisphere spring snow cover have continued to decrease in extent.
The rate of sea-level rise since the mid-nineteenth century has been larger than the mean rate during the previous two millennia. Over the period 1901–2010, global mean sea level rose by 0.19m (0.6 ft).
The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years, primarily from fossil-fuel emissions and secondarily from net land-use-change emissions.
Warming of the climate system is unequivocal. It is extremely likely (95%–99%) that human influence has been the dominant cause of the observed warming since the mid-twentieth century.
Continued emissions of greenhouse gases will cause further warming and changes in all the components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
Changes in the global water cycle will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase.
Global mean sea level will continue to rise. The rate of sea-level rise will exceed that observed during 1971–2010, due to increased ocean warming and increased loss of ice from glaciers and ice sheets.
Till now you might have been convinced that most of these environmental problems are due to human actions of the past hundreds of years. Similar factors are also responsible for different types of health issues emerging due to pollution. You have already read about pollution in details in Block - 3. Some of the health issues occurring due to pollution have also been discussed briefly in that block. You have studied about the definition of pollution in general and air pollution, water pollution, soil pollution etc. in specific. But can you define environmental pollution?
In simple terms, environmental pollution can be expressed as abnormal changes in physical, chemical, and biological characteristics of components present in the ecosystem namely air, water, and soil that can have harmful effects on various life forms including human beings. In this section, we will discuss health problems occurring due to air and water pollution.
Today environmental pollution is a major concern. Why is it so? This is because of rapid industrialization, urbanization, and carbon-centric economic development. This led to greenhouse gas emission, acid deposition, and waste generation to name a few. We have already discussed this in previous sections in detail. About 50 to 60 years back, most of these problems were limited to some specific localities. In other words, we can say these problems were mostly at a local scale. But today, with increasing magnitude and extent, these health issues have been occurring at regional and global scales. One of the major consequences of environmental pollution is the adverse impact on human health.
Therefore, today we are confronted with so many health problems created by environmental pollution. These increasing health problems need to be controlled. Before that, we should know the agents responsible for contamination, their sources, and emerging health risks.
Some of the major health risks emerged out of environmental pollution are listed in the table below:
| Agents of Contamination | Sources | Examples of Health Risks |
|---|---|---|
| Bacteria, protozoa, and parasites | Human excreta | Diarrhoea, dysentery, cholera, typhoid fever, ascariasis, schistosomiasis, polio |
| Viruses | Medical wastes containing body fluids from patients | HIV/AIDS infections and Hepatitis |
| Heavy/toxic metals | Industrial wastes and plastics | Continued and long-term ingestion of heavy metals can cause cancer and toxic effects |
| Smoke (very small airborne solid particles) | Vehicle emissions, domestic fires, and industrial emissions | Respiratory infections, pneumonia, and lung cancer (in severe cases) |
| Carbon monoxide | Vehicle emissions | Acute respiratory problems and death |
Do you know that we are losing millions of lives each year due to diseases and associated health problems emerging out of environmental pollution? Majority of the cases are from the developing countries in Africa, Asia, and South America. Let us understand the negative consequences of environmental pollution by analyzing the loss of human lives due to environmental pollution.
According to the World Health Organization (WHO) website article titled “Environment and Health in Developing Countries,” estimated global deaths from the most significant environmentally-related causes or conditions, and from certain diseases with a strong environmental component are as follows: