Energy, biodiversity and saving it

Who eats whom? Every food chain starts with plants. Ask yourself: if there were no grass and no grain, what would a goat or a hen eat? Plants and algae catch the Sun's energy by photosynthesis. They are the producers, at the base of the biome pyramid.

Above them come the eaters, level by level (each level is a trophic level):

• herbivores (plant-eaters): primary consumers;
• carnivores (meat-eaters): secondary consumers;
• top predators: tertiary consumers.

As you go up the pyramid, there are fewer living things, less biomass (total living matter) and less energy, because at each level much energy is lost as heat while living things go about their life processes. A simple way to picture it: if the plants hold 100 units of energy, the plant-eaters get about 10, and the meat-eaters about 1.

The book's biome pyramid (Fig. 2.10) also arranges biomes by climate: polar at the top, then subpolar, temperate and tropical at the bottom; cold at the top and hot at the bottom; wet on one side and dry on the other. So tundra sits at the top, rainforest at the wet bottom corner and desert at the dry one.

Biomes and living beings depend on each other. Biomes give plants, animals and people a home. In return, living beings change biomes: animals pollinate flowers and spread seeds; people turn land into farms and cities; tiny microorganisms break down dead matter and recycle nutrients.

Biodiversity means the variety of life: think of a simple meal with two dishes against a wedding feast with thirty; the feast has more diversity. Biodiversity includes the number of species, the genetic differences within a species, and the variety of habitats and natural processes that keep life going.

Life is not spread evenly over the Earth, so geography guides how we protect it:

• Hotspots: regions full of species found nowhere else, such as the Himalaya, the Western Ghats, North-East India and the Andaman and Nicobar Islands. Protecting them comes first.
• Ecosystem-based conservation: protect the whole place an animal lives in, not just the animal, with a plan that fits the place: mangroves on coasts, tree planting (afforestation) on mountains.
• Protected areas: national parks (strictest protection), wildlife sanctuaries (some human use such as grazing may be allowed), biosphere reserves and World Heritage Sites, chosen to keep key habitats whole and stop them being broken into pieces (fragmented).
• Barriers and corridors: rivers, mountains and valleys can block animals or give them paths; planners build wildlife corridors so animals can move and mix.
• People and land: sustainable ways of using land differ by place: terrace farming in the hills, agroforestry (trees with crops) in the plains.