December, with dominant northeast winds; The annual rainfall of the state is about of which 48 per cent is through the northeast monsoon, and 32 per cent through the southwest monsoon. Since the state is entirely dependent on rains for recharging its water resources, monsoon failures lead to acute water scarcity and severe drought. Tamil Nadu is divided into seven agro-climatic zones: northeast, northwest, west, southern, high rainfall, high altitude hilly, and Kaveri Delta (the most fertile agricultural zone). Flora and fauna There are about 2,000 species of wildlife that are native to Tamil Nadu. Protected areas provide safe habitat for large mammals including elephants, tigers, leopards, wild dogs, sloth bears, gaurs, lion-tailed macaques, Nilgiri langurs, Nilgiri tahrs, grizzled giant squirrels and sambar deer, resident and migratory birds such as cormorants, darters, herons, egrets, open-billed storks, spoonbills and white ibises, little grebes, Indian moorhen, black-winged stilts, a few migratory ducks and occasionally grey pelicans, marine species such as the dugongs, turtles, dolphins, Balanoglossus and a wide variety of fish and insects. Indian Angiosperm diversity comprises 17,672 species with Tamil Nadu leading all states in the country, with 5640 species accounting for 1/3 of the total flora of India. This includes 1,559 species of medicinal plants, 533 endemic species, 260 species of wild relatives of cultivated plants and 230 red-listed species. The gymnosperm diversity of the country is 64 species of which Tamil Nadu has four indigenous species and about 60 introduced species. The Pteridophytes diversity of India includes 1,022 species of which Tamil Nadu has about 184 species. Vast numbers of bryophytes, lichen, fungi, algae, and bacteria are among the wild plant diversity of Tamil Nadu. Common plant species include the state tree: palmyra palm, eucalyptus, rubber, cinchona, clumping bamboos (Bambusa arundinacea), common teak, Anogeissus latifolia, Indian laurel, grewia, and blooming trees like Indian laburnum, ardisia, and solanaceae. Rare and unique plant life includes Combretum ovalifolium, ebony (Diospyros nilagrica), Habenaria rariflora (orchid), Alsophila, Impatiens elegans, Ranunculus reniformis, and royal fern. National and state parks Tamil Nadu has a wide range of biomes extending east from the South Western Ghats montane rain forests in the Western Ghats through the South Deccan Plateau dry deciduous forests and Deccan thorn scrub forests to tropical dry broadleaf forests and then to the beaches, estuaries, salt marshes, mangroves, seagrasses and coral reefs of the Bay of Bengal. The state has a range of flora and