The term ‘environment’ is derived from the French verb environner, which means to surround, surroundings and something that surrounds. Environment is an English term, formed by two words, i.e., environ and ment, which means encircle or all-around. Thus, environment is a complex of many variables, which surround human as well as all other living beings.
The term ‘environment’ refers to a definable place, where an organism lives, including physical, biological, material and social aspects of surroundings. It is an aggregate of external conditions that influence the life, specifically the life of human being
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Generally speaking, the environment includes entire range of external influences or components, viz., physical or abiotic and biological or biotic forces of nature, which surround and influence organisms. Physical or abiotic components of environment are those components which consist of lithosphere (land), atmosphere (air) and hydrosphere (water), whereas biological or biotic components include flora, fauna and micro-organisms (Singh, 2009).
It has been, so far, clearly stated that environment is the assemblage of abiotic and biotic components, which influence all organisms on earth. This assemblage has always been changing in every geological era and is still changing continuously. Change is the law of nature. Every component of environment, which is presently found in whatsoever form, had a different state—quantity and quality—in the past. It has taken millions of years to reach the present condition.
Some of the environmental changes are very rapid, e.g., earthquake and volcano and some are very slow, e.g., glaciation or de-glaciation, biological succession, climate change, etc., which is a long process of change, i.e., hundred to millions of years. If these changes are minor and slow and various components of environment are able to keep pace with these changes, these do not adversely influence the inbuilt self-regulatory mechanism of environment.
These changes are, thus, counterbalanced by changes in other components of environment and eventually environmental stability is restored. Thus, there is a reciprocal and interactive relationship between different components of environment, e.g., impact of climatic change is clearly reflected in glacier retreat or advancement and primary succession on recently de-glaciated terrain.
The changes of various components of environment become problematic when the inbuilt self-regulatory mechanism of environment fails to establish environmental stability or equilibrium by changes in other components of environment. Also these changes become problematic when different components of environment are not able to adapt to these changes and adversely influence living organisms in general and human beings in particular.
Sometimes, these problems become so severe that they cause huge losses to all living beings. Some of these problems are global in nature such as climate change, ozone depletion, and some are regional such as deforestation and biodiversity loss and some are local such as water and air pollution.
Global and Indian Experiences:
Studies show that increasing human role in environment has changed and modified various components of environment to such an extent that these changes are adversely influencing living organisms in general and human beings in particular. Thus, these changes and modifications have become problems of various intensity and scale to mankind. Studies are also reporting that, human being are increasingly experiencing the adverse impacts of environmental changes across the globe, particularly the developing countries like India.
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Environmental changes can be studied in two ways:
(1) Different components of environment, e.g., abiotic and biotic are taken up and changes in these components are studied, and
(2) Some important examples of environmental changes, e.g., land use/cover change, climatic change, glacier retreat, modifications and changes in species composition, deforestation, degrading quality of air, water and land and soils, etc., are taken to study.
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The first approach is systematic one, while the second is problem-oriented. Both the approaches have their own advantages and disadvantages. First approach is, however, more scientific and comprehensive. Therefore, first approach is adopted in this book.
Following the first approach, environmental changes are initially divided into two categories, i.e., changes in abiotic and changes in biotic components. Changes in abiotic components are further divided into three categories viz., changes in lithosphere (degradation of soil and land, minerals, etc.), changes in atmosphere (composition of atmospheric gases, air quality, vapours, particle energy; changes in heat budget, global warming, greenhouse effect, air pressure, wind direction, cyclones, humidity and precipitations, etc.) and changes in hydrosphere (surface water discharge and its quality, ground water depletion and quality and oceanic water quality).
Similarly, changes in biotic components are further divided into flora, i.e., vegetation, fauna, i.e., animals and micro-organisms. Biotic components also include human population (Figure 1.1). However, detailed analysis of environmental changes is restricted to biodiversity and forests and extreme events only, since the main focus of the book is to study the biodiversity, its driving forces and management aspects. The following section describes the definitional aspects of biodiversity, its importance, state of biodiversity and its changes at global and Indian level, driving forces of biodiversity loss, etc., and various extreme events.
Biodiversity is simply understood as ‘diversity of species’. It is a specific quality of life on the earth. The dimensions and importance of biodiversity have just lately been realized due to which biodiversity of our planet has undergone severe alterations and modifications. Thus, the concept, knowledge and mass awareness about biodiversity is one of the most talked about subjects of 21st century.
Conservation and management of biodiversity has become an international slogan, especially after the signing of the Convention on Biological Diversity, 1992 (CBD) in Rio. Concern for biodiversity has received enormous attention in recent past because concern for biodiversity is actually the concern for human.
All forms of life—human, plants and animals—are so closely linked that disturbance in one gives rise to disturbance in other. If the species disappear or extinct, they signify degradation in the entire ecosystem, which of may threaten man’s own existence on the planet earth (Joshi and Joshi, 2004). Biodiversity has a great importance for human beings but before we deal with the importance and services of biodiversity, there is a need to understand what exactly biodiversity means.
World Convention on Biological Diversity (Article II of CBD, Earth Summit I; 1992) defined biological diversity as “the variability among living organisms from all sources including, inter-alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems”.
The term ‘biodiversity’ refers to the variety of life and its biological diversity on the earth. The number of species of plants, animals, micro-organisms, enormous diversity of genes in these species, different ecosystems; such as desert, rainforests and coral reef, all are part of biologically diverse earth.
Ervin (1991) defined biodiversity as “biodiversity is the product of organic evolution, that is, the diversity of life in all its manifestations”. Biological diversity is, thus, holistic and this is indicated in its very nature of the word’s root meaning; it is the sum of earth species including all their interactions and variations within their biotic and abiotic environment in both space and time.
Biodiversity is a very comprehensive term which reflects the diversity of organism at all levels from populational-genetical and geographical-diversity to species, to lineages, and higher taxonomic categories to ecological systems (Orians, 1986). While, according to Raven (1994), biodiversity is “the sum total of plants, animals, fungi and micro-organisms in the world including their genetic diversity and the way in which they fit together in communities and ecosystems”.
It is evident from above-stated definitions that the term ‘biodiversity’ is so diverse and vast that the complete definition is very difficult to derive. Takacs (1996), while defining biodiversity mentioned that “you are talking about a subject that is literally as large as the world itself.”
Thus, it can be said that biodiversity has very broad meaning. It has different meanings for different scientists having different backgrounds, e.g., environmentalists, biologists, bio-geographers, botanists, etc. Kirkland et al. (1990) suggest that biodiversity is not only the total of all native species in a particular region (species richness), but also the ecological roles of these species in ecosystems and genetic diversity contained within species population.
Noss and Larry (1986) mentioned that “biodiversity by definition forces us to consider many different species not just vertebrates, not just plant, but things that we do not see or understand nearly as well, such as bacteria and fungi and the process that ties these all together, the interrelationships between them. I think it forces us, if we do justice to the concept, it forces us to think much more broadly than we have in recent past”.
Thus, defining biodiversity in some words or statements is almost impossible. Joshi and Joshi (2004) conclude the term ‘biodiversity’ is used to cover both the number of different populations and species that exist and the complex interactions that occur among them.
To generalize, also widely accepted biodiversity is simply a variety of life and is manifested at three levels:
(a) Genetic diversity—it refers to the diversity within specie,
(b) Species diversity—it refers to the diversity among species, and
(c) Ecosystem diversity—it refers to the diversity of habitats.