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Traditionally, remote sensing encompasses a wide array of technologies and methods used to gather information about objects, areas, or phenomena without direct physical contact. This includes devices like seismographs, fathometers, radar systems, and more. These tools enable us to observe and measure various aspects of the environment from a distance.

However, in contemporary contexts, when we talk about remote sensing in a more specialized sense, we often refer to the use of satellite and aerial-based systems to capture and analyze electromagnetic radiation reflected or emitted from the Earth's surface. This form of remote sensing has become incredibly valuable in fields such as environmental monitoring, urban planning, agriculture, forestry, and disaster management, among others.

Modern remote sensing techniques leverage sensors capable of detecting specific wavelengths of electromagnetic radiation, such as visible light, infrared, and microwave radiation. By analyzing the patterns and intensity of this radiation, researchers can derive valuable information about the Earth's surface features, including vegetation cover, soil moisture, land use, and changes over time.

Global warming is the hottest issue facing life in our times. The gradual average increase in air temperatures near Earth’s surface over the past one to two centuries is leading to the phenomenon called global warming. It is this global phenomenon that triggers climate change, threatening the entire life on Earth. Earth’s climate has changed over all conceivable geological timescales, but that was all on account of the natural phenomenon. But, human activities are making the phenomenon more pronounced since the beginning of the Industrial Age, now emerging as a dominant triggering factor in influencing the overall climate fabric of the planet.

Radioactive pollution is largely attributable to radioactivity, a natural property of certain elements, such as radium, uranium, thorium, etc. of spontaneously emitting protons (alpha particles), electrons (beta particles), and gamma rays (short-wave electromagnetic waves) through the disintegration of their atomic nuclei (nuclides).

An alpha particle consists of two protons and two neutrons, which is akin to a helium nucleus. Alpha particles travel at a very slow speed, whereas gamma rays propagate at the speed of light. The alpha particles have less penetration power than the beta and gamma rays. In human tissues, alpha particles can penetrate up to a depth of about 0.005 to 0.008 cm. The gamma rays, on the other hand, are the most penetrating and can easily pass through a human body without striking anything in between. The high penetration power of gamma rays is because they have no charge; therefore, they do not interact with anything as the charged alpha particles would do

A sound is a form or energy. Therefore, it has to have an impact on life in one way or the other. Most of the organisms of Kingdom Animalia communicate with each other creating a peculiar sound. Creating sound is inevitable for performing various life activities. Every animal species has the characteristic sound it reflects through its behavior. Whatever all the animals communicate through creating specific sounds is all-natural. Nature, as such is a stupendous repository of a diversity of sounds, all being specific characteristics of life.

Human behavior, however, is highly evolved in terms of creating a variety of sounds. Communication, entertainment, and many behavioral activities are expressed through creating distinctive sounds. There is a difference between natural sounds and the ones human beings create or can create. Humans often generate sounds, not just in a natural manner, but also with various technical aids, that often become unpleasant what we call noise. Creating noise, or noise pollution, seems to be an exclusive characteristic of the human species. Of course, there could be some natural sounds that might occasionally cause havoc to life. Examples are the sounds generated at the time of the volcanic eruption, during an earthquake

Life on Earth is rooted in soil. Soil is not just a substratum anchoring the plants and giving a base for all terrestrial animals. It is the largest terrestrial ecosystem, and one of the most wonderful ecosystems on Earth. It inhabits most microorganisms. Microbial populations flourishing within the soil have greater biomass than all the human beings, elephants, and whales put together. It is due to the microorganisms that the soil constitutes the most active ecosystem on Earth.

The health of the soil is crucial for the health of all the plants growing on it and for all the animals dependent on it for their inhabitation and nourishment. Soil health is also critical for the well-being of numerous microorganisms, detritivores, and several other organisms. Soil is composed of all essential nutrients/ minerals, air, water, and organisms in a proportion that strikes its ecological balance and maintains its structure and functions revealed through its productive potential.

Soil, like all other ecosystems, is itself a dynamic ecosystem. Its composition keeps changing but natural inbuilt mechanisms help strike a balance and recover 

Ours is a Living Planet because ours is a Water Planet. The health of the Living Planet depends on the health of its water resources. Ironically, the health of its water resources is at stake. And so of its life! The waters of the Earth are in the grips of pollution. Much of the water is already polluted and the rest is increasingly becoming polluted. Water pollution, indeed, is one of the worst problems life on Earth is faced with. Water pollution is halting human progress and is phenomenally affecting all walks of human civilization. Water pollution is even putting a question mark on our sustainable future. This chapter presents the causes, magnitude, and consequences of water pollution and also suggests ways and means to prevent and control water pollution and also attempts to manage water resources.

Air or atmosphere constitutes one of the integral components of the environment. Among all the environmental components, the air has the highest fluidity. Therefore, the entry of a foreign substance into the air imparts a quick and severe effect on the health of the organisms. Air in the biosphere has a mixture of various gases in a dynamic proportion which is conducive to maintaining the health and sustenance of all living organisms. An alteration in the composition of the atmosphere beyond a certain limit adversely affects organisms’ health, and might even be of more serious consequences for life.

Air pollution, thus, is defined as the occurrence of undesirable gases (e.g., carbon monoxide, sulfur dioxide, etc.) or particles (e.g., suspended particulate matter) in such concentrations that are deleterious to terrestrial life (vegetation, animals, and human beings) and some physical assets, like buildings, statues, and monuments. Air pollution especially affects the health of human beings living in highly modified (anthropogenic) ecosystems, e.g., cities and industrial areas.

We are living in a world that is in a grim state of environmental disruptions. Callous developmental activities resulting in pollution of all environmental components and gradually culminating in global warming, climate change, and species extinction are responsible for triggering the processes of environmental disruption. Pollution of air, water, and soil is rapidly assuming alarming proportions.

The very processes of socioeconomic development are now posing threat to economic progress as well as to human health. Ominous changes in global climate are posing threat to life on Earth. The irony is that the major cause of environmental disruptions is anthropogenic rather than natural. Human’s materialistic progress and environmental pollution in our contemporary world go hand in hand.

ABSORPTION (of light): A process by which light is taken-up by another material. Examples include soot consisting of tiny black particles, which absorb all visible light; and nitrogen dioxide, a pollutant mostly from diesel and gasoline engines, that absorbs blue light resulting in air with a brown tint.

AIRBORNE SENSING: Remote sensing from an airplane. (Related words: airphoto, aerial)

ACCELERATED EROSION: Erosion in excess of natural rates, usually as a result of anthropogenic activities.

AERATION, SOIL: The exchange of air in soil with air from the atmosphere. The air in a well aerated soil is similar to that in the atmosphere; the air in a poorly aerated soil is considerably higher in carbon dioxide and lower in oxygen.

ACID SOILS: Acid soils with pH below 6.5 are widespread. Main limitations of these acid soils are low pH, low CEC, low status of bases, especially Ca, Mg, and K along with toxicity of Al and Mn. Use of acidifying fertilizers aggravates this situation.

ABSORPTION ACTIVE: Movement of ions and water into the plant root as a result of metabolic processes by the root, frequently against an electrochemical potential gradient.

ALLIC: soil family class term used in Oxisols as a calcareous and reaction class category. Soils placed in the allic class are acid and have low CEC with high amounts of KCl-extractable aluminum in a layer at least 30 cm thick within the control section. If used for agriculture, these Oxisols require large inputs of lime to displace the aluminum and raise pH.

ACID-FORMING FERTILIZER: A term applied to commercial fertilizers which leave an acid residue in the soil. The amount of calcium carbonate required to neutralize the acid residue is referred to its equivalent acidity.

AGRICULTURAL WASTE: The characteristics of the agricultural waste materials make them important in respect of their use and economic value. Agricultural wastes can he put to use because (1) Farm development (improvement of soil health, soil fertility, soil physical conditions and plant protection), it is the source of energy and power, (3) it acts as animal feed and fodder, (4) it is the human food

ACTIVATION ENERGY: The energy required before the reaction of concern will proceed. Often, heating will supply the needed energy. Enzymes or other catalysts lower the activation energy of a reaction.

ABIOTIC FACTORS: Environmental influences produced other than by living organisms for example, temperature, humidity, pH and other physical and chemical influences. Contrast it with ‘biotic factors’ - meaning effects due to biological components.

1. The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants. - Soil Science Society of America