The variety of life on earth, its biological diversity is commonly referred to as Biodiversity. The number of species of plants, animals and micro-organisms, the enormous diversity of genes in these species, the different ecosystems on the planet such as deserts, rainforests and coral reefs, are all part of a biologically diverse earth. Biodiversity boosts ecosystem productivity where each species, no matter how small, has an important role to play. Preserving species and their habitats is important for ecosystems to sustain themselves. It has long been feared that human activity is causing massive extinctions. Despite increased efforts at conservation, sustainability eludes.

The author Dr. M.A. Haque, a scientist by profession, through this book highlights the need for sustainable development and consumption, in order to avoid an ecological imbalance. Dr. Haque has authored a number of books on environment. With a keen eye for detail, he has provided the photographs for this book from his own collection.

The year 2010 was declared by the UN (United Nations) as "The International year of Biodiversity". Obviously, the purpose behind this move was to attract the attention of the world towards the biodiversity present on the Earth. The United Nations started the tradition of associating a particular year with a particular year with a particular theme in 1959. Since 1959 the UN has regularly designated International Years. The purpose is obvious. By assigning a theme to a whole year, attention of the entire world can be drawn towards the issue which can encourage international action to address concerns relating to the issue which is of global importance and ramifications. This way, year after year important issues have been brought to focus by the United Nations. But it is not so that every year since 1959 has been designated so. Certain years have been left out deliberately taking into account fiscal reasons and also to avoid trivialization of the exercise. 1959 was celebrated as the "World refugee Year", 1965 was declared as "International Cooperation Year", 1998 was declared as the "International Year of Ocean". The 2002 was declared as the "International Year of Mountains", 2003 was declared as the "International Year of Freshwater", 2006 was the "International Year of Deserts and Desertification", 2009 was celebrated as the "International Year of Natural Fibres". While 2011 was celebrated as the "International Year of Forests".

Following the same tradition during the year 2010 biodiversity continued to be in focus and various functions and programmes were organized all over the world to highlight the status of biodiversity, its value and threats faced by it. The activities also highlighted the possible actions which can conserve biodiversity on a global scale. Various programmes focused on different facets of biodiversity. The concluding function was held in Japan in the city of Kanazawa. The celebration focused on the achievements of the International Year of Biodiversity. Also, the occasion was used for contribution to the launch of the "International Year of Forests" i.e. The main goals of the International Year were of Biodiversity were to:

• Enhance public awareness of the importance of conserving biodiversity and of the underlying threats to biodiversity

• Raise awareness of the accomplishments to save biodiversity that have already been realized by communities and governments

• Promote innovative solutions to reduce the threats to biodiversity

• Encourage individuals, organizations and governments to take immediate steps to halt biodiversity loss

• Start dialogue between stakeholders for the steps to be taken in the post-2010 period.

At this point the question that arises is why the UN had to designate a year for biodiversity? In this regard it is important to understand Earth is a part of the larger solar system. If we look at the diagram of the solar system, it is located at the third position from Sun. In all, there are eight planets in the solar system and Earth is the largest one with highest mass and maximum density among the four planets which are called the terrestrial planets. These are Mercury, Venus, Earth and Mars. These planets are primarily made of silicate rocks. Earth is quite often called the Blue Planet as well. Reason is that the three fourth of the surface of Earth is covered by water mainly in the form of oceans and seas. Presence of water on the surface of Earth is a unique feature of Earth. On looking from the space the area looks blue in colour. If we take into account the quantity of water present in the oceans, it works out to about 1.35×1018 metric tons. In terms of volume it is about 1.38×109 cubic km. Most of the water present on Earth (about 97.5%) is saline. The rest i.e. about 2.5% is fresh water. In this regard it is important to note that most of the requirements for the living organisms and activities on the land part of Earth are met from fresh water. But all the fresh water present on Earth is not available. For example, about 70% of the fresh water is in the form of ice and a certain percentage of the fresh water is in deep rocks. As such these are not readily utilizable.

The oceans carry a heavy load of salts. About 3.5% of the ocean mass is due to the salts present there. These salts reached there either on account of volcanic activities or from igneous rocks. On account of the presence of salts in the sea water, there is salinity which makes sea water different from water. This differentiates the oceans as a habitat from water habitats like rivers, lakes, ponds, reservoirs etc. In addition to the salts, sea water holds large quantities of dissolved atmospheric gases. These gases are utilized by organisms living in the water for their activities. Water present in the oceans plays important role in deciding the Earth’s climate as well. The oceans can store huge quantity of heat and changes in the pattern of ocean temperature can lead to changes in the weather conditions in different parts of Earth.

Water in liquid form is known to exist only on Earth. This water is responsible for life on Earth. There is no organism which does not contain water and which can survive without water. Some of organisms may contain up to 95% or even more of water in terms of mass. Our own body which consists of various types of tissues including the hard bones consists of about 70% water. Water is regularly lost from the body of the organisms living outside water in liquid form or as vapour causing deficit of water in the body. This is the reason that all such organisms need to absorb water on regular basis. Larger animals do so by drinking water. Plants, microbes, and smaller animals satisfy their need by absorbing it through their body surface.

Earth is known to interact with various objects in the outer space, sun and moon included. Earth is not stationary. It moves around the sun and simultaneously it rotates on its own axis too. It completes its rotation around the sun in the same time when it completes its rotation on its axis 366.26 times. The time required to complete the rotation is 365.26 solar days. This is the reason why after every four years we have a leap year in our calendar. The solar calendar consists of 365 days. After every four year one day is added to February to compensate for the 0.26 extra day in the solar year. An important fact is that the axis of rotation of the Earth is not straight. It is tilted by 23.4° away from the vertical. This tilt is responsible for the seasonal variations that we experience on the Earth. Moon is the only known satellite which orbits around the Earth. Presence of the Moon is responsible for the tides that are generated in the oceans. Moon is also responsible for gradual slowing down of the rotation of the Earth. But it is an extremely slow process and we need not worry about it.

Earth is made of a thick outer solid layer which is called the mantle. Under the mantle there is a liquid layer called outer core and the inner most of the Earth is again solid. It is called inner core and it is mainly made of iron. The outermost or uppermost layer of the Earth is called the pedosphere. This is the part of Earth with which we regularly interact. It is composed of soil and we know that soil is the basis of all vegetation and agriculture. The soil provides support for anchorage to the plants. It is the storehouse of nutrients which are absorbed by plants and soil is the layer where water is stored to be absorbed by plants. From the plants the food materials and the nutrients reach the animal world including humans. A large fraction of water also reaches the animal body with the food obtained from plants. This is the reason that soil is considered very important for life on Earth and its degradation or loss is not good for the living organisms.

Soil is formed due to breaking of the rocks into smaller pieces. Breaking of the rocks takes place due to chemical processes and environmental changes on Earth’s surface. The process is generally called weathering or erosion. Once formed the soil is quite different from the parent rock or rocks from which it is formed. Reason is that soil does not consist of only the mineral particles coming from the rocks. The impact of water, atmosphere and living organisms play an important role in formation of soil and in determining its properties. Finally, it becomes a mixture of mineral materials derived from the rocks and organic matter coming from the living organisms. An important feature is soil has pore spaces between the particles. The pore spaces are responsible for keeping the soil has pre spaces between the particles. The pore spaces are responsible for keeping the soil porous and light. These pores hold water and air as well. The same water is utilized by plants for their survival. The water present in soil pores dissolves nutrients and other materials and helps in their absorption by plants. Air present in the pore spaces provides oxygen to the underground portions of plants. This is why very compact soil is not good for growth of plants. Farmers keep the soil porous by ploughing the land before seeding and by regular digging and turning it while the plants are growing.

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