Kerala’s 38,863 km˛ landmass (1.18% of India) is wedged between the Arabian Sea to the west and the Western Ghats—identified as one of the world's twenty-five biodiversity hotspots—to the east. Lying between north latitudes 8°18' and 12°48' and east longitudes 74°52' and 72°22', Kerala is well within the humid equatorial tropics. Kerala’s coast runs for some 580 km (360.4 miles), while the state itself varies between 35–120 km (21.74 - 74.56 miles) in width. Geographically, Kerala can be divided into three climatically distinct regions: the eastern highlands (rugged and cool mountainous terrain), the central midlands (rolling hills), and the western lowlands (coastal plains). Located at the extreme southern tip of the Indian subcontinent, Kerala lies near the centre of the Indian tectonic plate; as such, most of the state (notwithstanding isolated regions) is subject to comparatively little seismic and volcanic activity. Geologically, pre-Cambrian and Pleistocene formations compose t he bulk of Kerala’s terrain.
Eastern Kerala lies immediately west of the Western Ghats's rain shadow; it consists of high mountains, gorges and deep-cut valleys. Forty-one of Kerala’s west-flowing rivers—and three of its east-flowing ones—originate in this region. Here, the Western Ghats form a wall of mountains interrupted only near
Palakkad, where a pass known as the Palakkad Gap breaks through to provide access to the rest of India. The Western Ghats rises on average to 1,500 m (4921.26 ft)above sea level, while the highest peaks may reach to 2,500 m (8202.1 ft). Just west of the mountains lie the midland plains composing central Kerala; rolling hills and valleys dominate. Generally ranging between elevations of 250–1,000 m (820.2-3280.84 ft), the eastern portions of the Nilgiri and Palni Hills include such formations as Agastyamalai and Anamalai.
Kerala’s western coastal belt is relatively flat, and is criss-crossed by a network of interconnected brackish canals, lakes, estuaries, and rivers known as the Kerala Backwaters. Lake Vembanad—Kerala’s largest body of water—dominates the Backwaters; it lies between
Alappuzha and Kochi and is more than 200 km˛ in area. Around 8% of India's waterways (measured by length) are found in Kerala. The most important of Kerala’s forty-four rivers include the Periyar (244 km), the Bharathapuzha (209 km), the Pamba (176 km), the Chaliyar (169 km), the Kadalundipuzha (130 km) and the Achankovil (128 km). The average length of the rivers of Kerala is 64 KM, with only four longer than 16KM.Most of the remainder are small and entirely fed by monsoon rains. These conditions result in the nearly year-round water logging of such western regions as Kuttanad, 500 km˛ of which lies below sea level. As Kerala's rivers are small and lack deltas, they are more prone to environmental factors. Kerala's rivers face many pr oblems, including summer droughts, the building of large dams, sand mining, and pollution.
With 120–140 rainy days per year, Kerala has a wet and maritime tropical climate influenced by the seasonal heavy rains of the Southwest Summer Monsoon. In eastern Kerala, a drier tropical wet and dry climate prevails. Kerala's rainfall averages 3,107 mm annually; the all-India average is 1,197 mm. Some of Kerala's drier lowland regions average only 1,250 mm; the mountains of eastern
Idukki district receive more than 5,000 mm of orographic precipitation, the highest in the state. Kerala's rains mostly result from monsoons; more anomalous factors resulted in the red rains of 2001. Kerala . In summers, most of Kerala is prone to gale-force winds, storm surges, cyclone-related torrential downpours, occasional droughts, and rises in sea level and storm activity resulting from global warming. Kerala’s maximum daily temperature averages 36.7 °C; the minimum is 19.8 °C. Mean annual temperatures range from 25.0–27.5 °C in the coastal lowlands to 20.0–22.5 °C in the highlands.
Much of Kerala's notable biodiversity is concentrated and protected in Agasthyamalai Biosphere Reserve in the eastern hills. Almost a fourth of India's 10,000 plant species are found in the state. Among the almost 4,000 flowering plant species (1,272 of which are endemic to Kerala and 159 threatened) are 900 species of highly-sought medicinal plants. Its 9,400 km˛ of forests include tropical wet evergreen and semi-evergreen forests (lower and middle elevations—3,470 km˛), tropical moist and dry deciduous forests (mid-elevations—4,100 km˛ and 100 km˛, respectively), and montane subtropical and temperate (shola) forests (highest elevations—100 km˛). Altogether, 24% of Kerala is forested. Two of the world’s Ramsar Convention-listed wetlands—Lake Sasthamkotta and the Vembanad-Kol wetlands—are in Kerala, as well as 1455.4 km˛ of the vast Nilgiri Biosphere Reserve. Subjected to extensive clearing for cultivation in the 20th century, much of Kerala's forest cover is now protected from clearfelling. Keral a's faun a are notable for their diversity and high rates of endemism: 102 species of mammals (56 of which are endemic), 476 species of birds, 202 species of freshwater fishes, 169 species of reptiles (139 of them endemic), and 89 species of amphibians (86 endemic). These are threatened by extensive habitat destruction (including soil erosion, landslides, salinization, and resource extraction).
Eastern Kerala’s windward mountains shelter tropical moist forests and tropical dry forests, which are common in the Western Ghats. Here, sonokeling (Indian rosewood), anjili, mullumurikku (Erythrina), and Cassia number among the more than 1,000 species of trees in Kerala. Other plants include bamboo, wild black pepper, wild cardamom, the calamus rattan palm (a type of climbing palm), and aromatic vetiver grass (Vetiveria zizanioides). Living among them are such fauna as Asian Elephant, Bengal Tiger, Leopard (Panthera pardus), Nilgiri Tahr, Common Palm Civet, and Grizzled Giant Squirrel. Reptiles include the king cobra, viper, python, and crocodile. Kerala's birds are legion—Peafowl, the Great Hornbill, Indian Grey Hornbill, Indian Cormorant, and Jungle Myna are several emblematic species. In lakes, wetlands, and waterways, fish such as kadu (stinging catfish and choottachi (orange chromide—Etroplus maculatus; valued as an aquarium specimen) are found.
Much of Kerala's notable biodiversity is concentrated and protected in Agasthyamalai Biosphere Reserve in the eastern hills. Almost a fourth of India's 10,000 plant species are found in the state. Among the almost 4,000 flowering plant species (1,272 of which are endemic to Kerala and 159 threatened) are 900 species of highly-sought medicinal plants. Its 9,400 km˛ of forests include tropical wet evergreen and semi-evergreen forests (lower and middle elevations—3,470 km˛), tropical moist and dry deciduous forests (mid-elevations—4,100 km˛ and 100 km˛, respectively), and montane subtropical and temperate (shola) forests (highest elevations—100 km˛). Altogether, 24% of Kerala is forested. Two of the world’s Ramsar Convention-listed wetlands—Lake Sasthamkotta and the Vembanad-Kol wetlands—are in Kerala, as well as 1455.4 km˛ of the vast Nilgiri Biosphere Reserve. Subjected to extensive clearing for cultivation in the 20th century, much of Kerala's forest cover is now protected from clear felling. Kerala's fauna are notable for their diversity and high rates of endemism: 102 species of mammals (56 of which are endemic), 476 species of birds, 202 species of freshwater fishes, 169 species of reptiles (139 of them endemic), and 89 species of amphibians (86 endemic). These are threatened by extensive habitat destruction (including soil erosion, landslides, salinization, and resource extraction).
Eastern Kerala’s windward mountains shelter tropical moist forests and tropical dry forests, which are common in the Western Ghats. Here, sonokeling (Indian rosewood), anjili, mullumurikku (Erythrina), and Cassia number among the more than 1,000 species of trees in Kerala. Other plants include bamboo, wild black pepper, wild cardamom, the calamus rattan palm (a type of climbing palm), and aromatic vetiver grass (Vetiveria zizanioides). Living among them are such fauna as Asian Elephant, Bengal Tiger, Leopard (Panthera pardus), Nilgiri Tahr, Common Palm Civet, and Grizzled Giant Squirrel. Reptiles include the king cobra, viper, python, and crocodile. Kerala's birds are legion—Peafowl, the Great Hornbill, Indian Grey Hornbill, Indian Cormorant, and Jungle Myna are several emblematic species. In lakes, wetlands, and waterways, fish such as kadu (stinging catfish and choottachi (orange chromide—Etroplus maculatus; valued as an aquarium specimen) are found.