Biodiversity is the incredible, dizzying variety of life that surrounds us, including all of the earth’s plants, animals, their habitats, and the natural processes that they are a part of. 
The concept includes every species of bacteria, virus, plant, fungi, and animal, as well as the diversity of genetic material within each species. It also encompasses the diverse ecosystems the species make up and the ongoing evolutionary processes that keep them functioning and adapting. 
The natural world – biodiversity – provides us with food, materials and energy. We eat animals and plants; insects pollinate many of the foods we consume; microbes in the soil provide the nutrients the plants need to grow; vegetation and soil biodiversity reduce flooding and release clean drinking water; vegetation soaks up a substantial proportion of the climate warming carbon dioxide gasses that we emit. The list goes on and on. 
These benefits are known as ecosystem services.
A functioning natural world provides a living for farmers, fishers, timber-workers and tourism operators to name but a few. 
Medicines originating from wild species, including penicillin, aspirin, taxol, and quinine, have saved millions of lives and alleviated tremendous suffering. 40% of all prescriptions are for medicines that originated from plants and animals. No one knows how many more cures await discovery, hidden in Earth’s poorly studied species.
There are 80,000 species of edible plants known on Earth, but 90% of the world’s food comes from a mere 20 of these species. Edible plant species, both those we know of and those we don’t, offer a tremendous resource of possibilities that could greatly add to the security of our food. How many of these have high potential for commercial exploitation and for feeding the hungry? Certainly a great many.
Biodiversity is the life support system of our planet- we depend on it for the air we breathe, the food we eat, and the water we drink. Wetlands filter pollutants from water, trees and plants reduce global warming by absorbing carbon, and bacteria and fungi break down organic material and fertilize the soil. It has been empirically shown that native species richness is linked to the health of ecosystems, as is the quality of life for humans.
The connections between biodiversity and our sustainable future appear closer and closer the more we look. We literally need to conserve biodiversity like our lives depend on it! 
So biodiversity keeps us alive, but there are other less tangible benefits.
Recreation such as fishing or hiking, the aesthetic beauty of the natural world and our spiritual connection with nature; the cultural values we place on plants and animals such as the kangaroo and emu on the Australian coat of arms – these are all benefits of biodiversity.
Research suggests that natural environments have direct and positive impacts on human well-being, despite the highly-urbanised modern lifestyles that most of us live. Mental-health benefits from exercising in natural environments have been are greater than those gained by exercising in the synthetic environment of the gym. Mood and self-esteem benefits are even greater if water is present.
The value that humans gain from biodiversity reminds us that, despite being predominantly urban, we are still intrinsically part of the natural world. We are a component of and therefore dependent on the ecosystem. This has led to the global concerns around anthropogenic biodiversity loss.
Biodiversity in decline
Changes in surrounding biodiversity affect all of us. Unlike other species however, we have the chance to determine what these effects might be.Globally, biodiversity is in rapid decline. The explosion of the human population from 2 to 7 billion in just 100 years has caused the extinction of many species.
Scientists agree that the earth is experiencing its first anthropogenic climate-driven global extinction event. They also agree that this is happening at a rate too fast for species to adapt.
This loss of biodiversity is concerning because of the growing consensus that it goes hand-in-hand with a reduction in the stability and productivity of ecosystems. The result may be that the services on which we rely could be compromised in damaging ways.  Urban and rural citizens alike rely on these natural products and benefits.
In the long term, the value of services lost may greatly exceed the short-term economic benefits that are gained from transforming ecosystems. When we modify an ecosystem to improve a service it provides, this generally also results in changes to other ecosystem services. For example, actions to increase food production can lead to reduced water availability in terms of quantity and quality for other users. This can result in the degradation of many services, such as fisheries, water supply, and protection against natural hazards, seriously affecting people’s well-being. 
The UN’s The Economics of Ecosystems and Biodiversity (Teeb) shows that the real cost of damaging nature … is at least 10 times greater than the cost of maintaining the ecosystem as it is so that we can reap the associated benefits. For example: close to the University of York the costs of flood defence construction and flood-related insurance claims in the Vale of York hugely outweigh the agricultural benefits of drainage ditches and overgrazing in the River Ouse catchment. Rather than treating nature as a pleasant luxury, Teeb argues that we should integrate the real costs and benefits within our decision-making. It should not be the preserve solely of environment and conservation ministries, but it should be at the core of the activities of finance departments.
Teeb argues that we should get rid of subsidies that are environmentally damaging and reward beneficial activities that maintain natural ecosystems. This might be by including the costs of damage within the purchase price of products to encourage us to buy the least damaging items, and potentially by paying land owners and countries directly to maintain natural ecosystems. Farmers in the Ouse catchment have recently received payments for blocking their drainage ditches; and the perverse subsidies that rewarded farmers by the animal – resulting in over-grazing, trampling and erosion – have been removed.
If you keep microscopic predators and prey in a small bottle, the predator usually becomes too common, eats most or all of the prey, and then dies out itself. The planet is our bottle: 7 billion people and counting, 2 billion more by the middle of this century, with the level of consumption per person increasing just as fast. Greening the world’s economies and social systems is essential is we are to avoid a similar collapse. 
TRY PLANTING NATIVE PLANTS IN YOUR GARDEN, WHAT NATIVE FOOD PLANTS ARE YOU AWARE OF, CAN YOU MAKE A SANCTUARY FOR SOME NATIVE WILDLIFE IN YOUR BACK YARD?
 http://www.theguardian.com/environment/cif-green/2010/may/21/why-care-about-biodiversity (22 May 2010)
 http://theconversation.com/explainer-what-is-biodiversity-and-why-does-it-matter-9798 (12 October 2012)