Nature · Ecology · 15 min read

The Ecological Hotspots of Idukki: Kerala's Mountain Heartland

From Anamudi's grassy summit to the cactus scrub of Chinnar, from shola forests to the tiger country of Periyar, Idukki holds more kinds of wild landscape than any other district in Kerala. A guide to its ecological hotspots: what makes each one special, what lives there, and what threatens them.

By GK Global, Adimali, Munnar · Trails & Tales by GK

Idukki is Kerala's mountain district. Almost all of it lies in the Western Ghats, one of the world's great biodiversity hotspots and a UNESCO World Heritage Site since 2012. Within its borders the land rises from about 300 m in the river valleys of the west to 2,695 m on the summit of Anamudi, the highest point in India south of the Himalaya, and falls again into the dry rain-shadow valleys on the Tamil Nadu border. Few places of its size hold such a range of habitats: evergreen rainforest, montane grassland, shola forest, moist and dry deciduous forest, thorn scrub, sandalwood forest, cardamom forest, rivers and great reservoirs.

This article is a guide to the most important of these places, the ecological hotspots of Idukki: why they matter, what lives there, and what threatens them.

A good place to start: the Neelakurinji Biodiversity Knowledge Centre

Before setting out, visitors can get an overview of the whole district at the Neelakurinji Biodiversity Knowledge Centre at Adimali, the gateway to Munnar. Housed at the Government High School, Adimali, it was set up by the Haritha Keralam Mission, the United Nations Development Programme (UNDP) and the Idukki district panchayat, growing out of a UNDP eco-restoration project, and was opened in September 2023. It is a permanent display on the biodiversity and cultural life of Idukki, with:

• 3D models of evergreen forest;
• a 3D map of the biodiversity hotspots around Munnar, with their plants, animals, birds, fish and reptiles;
• the houses and household things of the Muthuvan tribal community;
• 25 display panels on places across Idukki district;
• touchscreen kiosks with more than 50 short videos and games.

Visiting: open 9 am to 5 pm, closed on Mondays; entry ₹20 for adults and ₹10 for children (as announced at the opening; please check locally). Our video below takes you through the centre.

▶ Video: A Journey Into Nature's Tapestry: the Neelakurinji Biodiversity Knowledge Center

A walk through the Neelakurinji Biodiversity Knowledge Centre at Adimali, a permanent display on the forests, wildlife and tribal life of Idukki. More in our video gallery

Why Idukki is so rich

Three things make Idukki exceptional. The first is altitude: the High Ranges around Munnar form the highest mountain block in peninsular India, cool enough for plants and animals found nowhere at lower levels. The second is the rain: the southwest monsoon drenches the western slopes, while the mountains block it from the eastern valleys, so that a short drive can take you from dripping rainforest to dry scrub. The third is isolation: the high peaks are "sky islands", cut off from similar habitats elsewhere for thousands of years, where many species have evolved that live nowhere else on Earth.

1. Eravikulam National Park and Anamudi

The rolling grassland plateau of Eravikulam, about 97 km² just north of Munnar, is the best-known ecological treasure of Idukki. Above 2,000 m, its grasslands are dotted with dark pockets of shola forest in the folds of the hills. It holds the world's largest population of the Nilgiri tahr, the endangered mountain goat of the Western Ghats, found nowhere else on Earth, as well as many endemic plants, frogs, butterflies and birds such as the Nilgiri pipit. Every twelve years the slopes turn blue with the flowering of neelakurinji; the last mass bloom was in 2018, and the next is expected around 2030. Anamudi itself rises at the southern end of the park.

(Read more: Eravikulam National Park, the Nilgiri tahr and neelakurinji.)

2. The shola national parks: Mathikettan, Anamudi and Pampadum

Shola forests are stunted, evergreen montane forests that grow in the sheltered valleys of the high grasslands. They act as sponges, soaking up the monsoon rain and releasing it slowly into the streams through the dry months. In 2003, three small shola national parks were notified around Munnar: Mathikettan Shola (about 12.8 km²), near Poopara, an important elephant corridor; Anamudi Shola (about 7.5 km²), near Marayoor; and Pampadum Shola (about 1.3 km²), on the road to Vattavada, one of the smallest national parks in India. Small as they are, they protect some of the most important water sources and wildlife links in the High Ranges.

(Read more: The shola national parks of Munnar.)

3. Kurinjimala Sanctuary and the Vattavada grasslands

East of Munnar, around Kottakamboor and Vattavada, the Kurinjimala Sanctuary (about 32 km²) was declared in 2006 to protect the core habitat of the neelakurinji. It is a key link in the High Range landscape, joining Eravikulam and Anamudi Shola to the west, Pampadum Shola to the south, Chinnar to the northwest and the forests of Tamil Nadu to the east. The high grasslands here also shelter elephants, gaur, Nilgiri tahr and many endemic plants. Large areas around it have been planted with exotic eucalyptus and wattle, which dry out the land and crowd out the grasslands, and their removal is a major conservation task.

(Read more: Andavar Kovil, Vattavada.)

4. Chinnar Wildlife Sanctuary: the rain shadow

Just 60 km from Munnar, Chinnar Wildlife Sanctuary (about 90 km², declared in 1984) feels like another world. Lying in the rain shadow of the Western Ghats, it receives only about 500 mm of rain a year, a tenth of what falls on the western slopes. Its landscape runs from thorny scrub, with cactus and dry deciduous forest in the east, up to grassland and shola on the high western ridges. It is the stronghold in Kerala of the grizzled giant squirrel, a threatened species found only in South India and Sri Lanka. It has India's only rehabilitation centre for the Indian star tortoise and Kerala's largest population of mugger crocodiles in the Chinnar and Pambar rivers. Surveys have recorded some 963 flowering plants, 225 birds, 52 reptiles and 156 butterflies. Muthuvan and Pulaya communities live in settlements inside the sanctuary. The Thoovanam waterfall on the Pambar lies within it.

(Watch: Thoovanam Waterfalls. Read more: The waterfalls of Idukki.)

5. Marayoor: sandalwood country

The broad valley of Marayoor and Kanthalloor, also in the rain shadow, holds the only natural sandalwood forest in Kerala. Sandalwood is a partial parasite that grows best in dry, rocky country, and the Marayoor trees are prized for their high oil content. The valley is also a cultural landscape of great age, with Iron Age dolmens and rock paintings, and its farms grow sugarcane, vegetables and temperate fruit. The Pambar river, flowing east from the High Ranges, runs through the valley on its way to the Kaveri.

(Read more: The sandalwood forest of Marayoor, Marayoor's dolmens and Marayoor jaggery.)

6. Meesapulimala, Kolukkumalai and the high peaks

Beyond Eravikulam, the high ridges of the Kannan Devan Hills continue in a chain of grassland summits. Meesapulimala, at about 2,640 m the second-highest peak in the Western Ghats, and Kolukkumalai, on the border with Tamil Nadu, are part of the same sky-island grassland and shola system, home to Nilgiri tahr, endemic frogs and rare plants. These fragile grasslands are easily damaged by fire, trampling and invasive plants.

(Read more: Meesapulimala, Kolukkumalai and Karinthiri Malai.)

7. Periyar Tiger Reserve and the Cardamom Hills

In the south of the district, the Periyar Tiger Reserve around Thekkady covers about 925 km² of evergreen and deciduous forest, grassland and the great lake formed by the Mullaperiyar dam. It is one of India's best-protected tiger reserves, with tigers, elephants, gaur, Nilgiri tahr on its cliffs, lion-tailed macaques and a remarkable variety of birds, fish and amphibians. The Periyar river rises in the hills of the reserve.

Around it lie the Cardamom Hills, where for two centuries cardamom has been grown in the shade of natural forest trees under the Cardamom Hill Reserve, created by the rulers of Travancore. This shaded cardamom forest produces most of India's cardamom and still holds much of the region's biodiversity, but felling of shade trees, conversion to other crops and encroachment have long been a concern, and the reserve has been the subject of cases in the Supreme Court and the Kerala High Court.

(Read more: Periyar Tiger Reserve and the Mullaperiyar dam.)

8. Idukki Wildlife Sanctuary and the reservoirs

In the heart of the district, around the Idukki arch dam, lies the Idukki Wildlife Sanctuary, declared in 1976. It covers about 105 km², including about 33 km² of reservoir water held by the Idukki, Cheruthoni and Kulamavu dams, at heights of 450 to about 1,270 m. Its forests shelter elephants, gaur, sambar, dholes, Nilgiri langurs and the great hornbill, and a 2019 survey recorded 182 species of butterfly. In summer, as the water falls, islets such as Vairamani appear in the reservoir and become breeding grounds for birds.

(Read more: Pallivasal, Kerala's first hydroelectric project.)

9. Mankulam, the river valleys and the elephant corridors

Between the high plateau and the plains, the forests of Mankulam, the Anakulam valley, Adimali and the Periyar valley form a belt of evergreen and moist deciduous forest that connects the High Ranges with the lowland forests of Thattekkad and the Pooyamkutty and Edamalayar valleys. At Anakulam, wild elephants come down openly to drink at a spring in the river. These middle forests are rich in hornbills, waterfalls and endemic fish and frogs, and they form vital corridors for elephants moving between the hills and the plains.

(Read more: Thattekkad Bird Sanctuary, hornbills of Kerala and the wild animals of the Western Ghats.)

The wildlife of Idukki in brief

• Mammals: Asian elephant, tiger, leopard, gaur, sambar, Nilgiri tahr, dhole, sloth bear, lion-tailed macaque, Nilgiri langur, grizzled giant squirrel, Nilgiri marten and many small mammals and bats.
• Birds: high-altitude endemics such as the Nilgiri pipit, Nilgiri flycatcher, Palani laughingthrush, white-bellied sholakili and black-and-orange flycatcher; hornbills, Malabar trogons and the white-bellied treepie in the lower forests.
• Amphibians and reptiles: dozens of endemic frogs, many discovered only in recent decades, and shieldtail snakes, lizards and the star tortoise in the dry east.
• Insects: hundreds of species of butterflies and moths, from the tiny grass blues of the high grasslands to the Atlas moth and the Southern Birdwing.
• Plants: neelakurinji and other Strobilanthes, rhododendrons, orchids, balsams, and the trees of the shola and rainforest.

(Read more: Birds of the Western Ghats, the white-bellied treepie, butterflies and moths, cicadas and flowering trees through the seasons.)

Threats to Idukki's ecology

• Fragmentation and encroachment: roads, settlements, plantations and illegal land conversion have broken up forests and corridors. (Read: Land encroachment in Munnar.)
• Invasive plants: eucalyptus, wattle and pine plantations, and weeds such as lantana, have spread over grasslands and forest edges, drying the soil and pushing out native plants.
• Landslides and floods: steep slopes, heavy rain and changes in land use make Idukki prone to landslides, as the floods of 2018 and the Pettimudi landslide of 2020 showed.
• Human-wildlife conflict: as habitats shrink, elephants, gaur and other animals come into conflict with farmers and settlements. (Read: Human-wildlife conflict around Munnar and the story of Arikkomban.)
• Climate change: warming threatens the cold-adapted species of the high peaks, which have nowhere higher to go. (Read: Climate change in Munnar.)
• Fire and tourism pressure: grassland fires, often started by people, and crowds at fragile sites can do lasting damage. (Read: The Kurangani forest fire.)

Protecting the hotspots: the Gadgil and Kasturirangan reports

In 2011, the Western Ghats Ecology Expert Panel, chaired by the ecologist Madhav Gadgil, recommended dividing the Western Ghats into zones of different ecological sensitivity, with limits on quarrying, mining, large dams and polluting industries. Much of Idukki fell within the most sensitive zones. The report met fierce opposition in Kerala, especially in Idukki, where farmers and settlers feared for their land and livelihoods, and the Kerala Assembly urged the central government to reject it. A second committee under K. Kasturirangan (2013) proposed a much smaller ecologically sensitive area, excluding settlements and plantations, but this too was opposed in Idukki, and the final notification of the Western Ghats' ecologically sensitive areas has been delayed for years. After the floods and landslides since 2018, the debate over how to protect Idukki's fragile slopes while securing the lives of its people remains one of the most important questions facing the district.

Visiting responsibly

• Enter protected areas only through official entry points, guided walks and treks run by the Forest Department and eco-development committees.
• Do not light fires, leave plastic or pick plants, especially neelakurinji.
• Keep a safe distance from elephants and other wild animals, and never feed them.
• Stay on paths in the grasslands, which recover slowly from trampling.

(Read more: Munnar's environment, Munnar's wildlife, and our introduction to Munnar.)