In 1928, the location on the Kunthipuzha River at Sairandhri was identified as an ideal site for electricity generation, and in 1958 a study and survey of the area was conducted and a hydroelectric project of 120 MV costing Rs.

In 1976 the Kerala State Electricity Board announced plans to begin dam construction and the issue was brought to public attention.

On 1 September 1986 Silent Valley National Park was designated as the core area of the Nilgiri Biosphere Reserve.

[7] The Kerala Minister for Electricity called The Pathrakkadavu dam (PHEP) an "eco-friendly alternative" to the old Silent Valley project.

On 15 November, Minister for Forest Binoy Viswam said that the proposed buffer zone for Silent Valley would be declared soon.

[9] On 21 February 2007 ex-Chief Minister A. K. Antony told reporters after a cabinet meeting that "when the Silent Valley proposal was dropped, the centre had promised to give clearance to the Pooyamkutty project.

[citation needed] In addition, illegal activities such as ganja (Cannabis sativa) cultivation has caused habitat degradation.

[13] On 21 November 2009, Union Minister of Forest and Environment Jairam Ramesh and Kerala Forest Minister Binoy Viswam declared, while inaugurating the silver jubilee celebration of Silent Valley National Park in Palakkad, that the buffer zone of the Park would be made an integral part of it in order to ensure better protection of the area.

The Cabinet also sanctioned 35 staff to protect the area and two new forest stations in Bhavani range at Anavai and Thudukki.

The proposed buffer zone will have 94 km2 in Attappady Reserve Forest east of the Kunthipuzha and 54 km2 taken from the Mannarkaad range and Nilambur south division west of the river.

The underlying rock in the area is granite with schists and gneiss, which give rise to the loamy laterite soils on slopes.

The main tributaries of the river, Kunthancholapuzha, Karingathodu, Madrimaranthodu, Valiaparathodu and Kummaathanthodu originate on the upper slopes of the eastern side of the valley.

[22] The park being completely enclosed within a ring of hills, has its own micro-climate and probably receives some convectional rainfall, in addition to rain from the two monsoons.

In the remaining months, condensation on vegetation of mist shrouding the valley is estimated to yield 15 per cent of the total water generated in the rainforest.

The 2006 winter bird survey discovered the long-legged buzzard, a new species of raptor at Sispara, the park's highest peak.

[29] Distribution and demography of all diurnal primates were studied in Silent Valley National Park and adjacent areas for a period of three years from 1993 to 1996.

Of these, the Nilgiri langur was randomly distributed, whereas the lion-tailed macaque troops were confined to the southern sector of the Park.

The Silent Valley forest remains one of the most undisturbed viable habitats left for the endemic and endangered primates lion-tailed macaque and Nilgiri langur.

[30] Tiger, leopard, leopard cat, jungle cat, common palm civet, small Indian civet, brown palm civet, ruddy mongoose, stripe-necked mongoose, dhole, clawless otter, sloth bear, small Travancore flying squirrel, Indian pangolin (scaly anteater), porcupine, wild boar, sambar, spotted deer, barking deer, mouse deer, elephant and gaur also live here.

[34] A survey jointly conducted by Indian Dragonfly Society and the Forest and Wildlife Department in September 2018 in the buffer zone of the Silent Valley National Park found 82 species of odonata.

The species found include Indosticta deccanensis, Burmagomphus laidlawi, Microgomphus souteri, Onychogomphus nilgiriensis, Euphaea dispar, Idionyx travancorensis, Megalogomphus hannyngtoni and Lestes dorothea.

The species studied were Palaquium ellipticum, Cullenia exarillata, Poeciloneuron indicum, Myristica dactyloides, Elaeocarpus glandulosus, Litsea floribunda, Mesua nagassarium, Cinnamomum malabatrum, Agrostistachys meeboldii, Calophyllum polyanthum, Garcinia morella and Actinodaphne campanulata.

[43] Throughout human history about 10% of the genetic stock found in the wild has been bred into palatable and higher yielding cereals, fruits and vegetables.

Future food security depends on the preservation of the remaining 90% of the stock through protection of high biodiversity habitats like Silent valley.

An important example of use of wild germplasm is gene selection from the wild varieties of rice Oryza nivara (Central India) and Oryza Pittambi found in Silent Valley for the traits of broad spectrum disease resistance in high yielding hybrid rice varieties including IR-36, which are responsible for much of the Green Revolution throughout Asia.

[46] Also, genetic evaluation of plant growth promoting Rhizobacteria obtained from Silent Valley indicated that strain, IISR 331, could increase the growth of black pepper cuttings by 228% and showed 82.7% inhibition of the common plant wilting disease Phytopthora capsici in laboratory tests (in vitro).

People engaged in grazing livestock often burn an area to get fresh grass shoots for their cattle, especially during dry season when fire danger is greatest.

[51] The cannabis mafia has cut hundreds of acres of evergreen tropical forest in the Attappady Hills, including Silent Valley buffer zones, for illegal cultivation of the cash crop.

[13] The ticket counter of the Silent Valley National Park at Mukkali was attacked by a group of Maoists in December 2014.

A big contingent of special police has been deployed there since then, but the growing influence of Maoist groups in tribal east Kerala is of grave concern.