Agumbe, water issues and Acacia

Agumbe in Shivamogga district, known as Cherrapunji of the South, was in news recently for water scarcity (DH, Apr 11). Agumbe and Bhagavathi valley areas receive unusual rainfall of around 7,000 mm in a year. Nearly 80% of this is from June to August. The months of November to March are usually dry months.

At the height of summer, the temperature in the open rises immensely and soil becomes bone dry in these months. The seeds from adjoining forest patches do give rise to seedlings in these grass lands, but the intense competition from the matty of roots of grasses and the recurrent annual fires kill these seedlings. This is the reason that native species cannot come up in the open, in these grass lands. Use of Acacia as a cover crop has been a success in raising the native species.

I have known the tract for the past over 40 years and have laid out research plots in 1976-77 at Hosur near Agumbe, using 38 different species, mostly native. Among the species tried, only Acacia auriculiformis and Casuarina survived in the long run. The objective of research trial was afforestation of man-made grass lands, initially with which ever species that can come up, and later use that as a nurse crop for regeneration of natural forest species.

In early 1980s under-planting in some Acacia plantations was done with cane (Nagabettha), with very good success. In 1984, another 23 native species from evergreen forests were used in under-planting at Solur near Thirthahalli town. Around 10 species like Balagi, Saldhupa, Kiralbogi etc have done well. Acacia has improved the soil nutrient and water status of the sites.

Acacia was first brought from Australia and introduced in Midnapore district of West Bengal in 1920s for afforestation of coastal barren areas. In Karnataka, its first introduction was in Ayanur village of Shivamogga in 1966. In 1972, we used it as a fire break along the periphery in rubber plantations in Puttur (Dakhin Kannada). Some well grown trees are existing even today.

In order to get a feel of the difficulties in raising native species, the Forest Department offered scientists of Indian Institute of Science the native species of their choice to be grown for afforestation of these grass lands. They undertook planting in 4 hectares at Murur–Kalabbe village in Kumta taluk in 1990, in a coastal afforestation area, but the success of native species was very poor as compared to that of  Acacia. Some of the native species did survive, but their growth was very poor.

Native species

Similarly, the Kudremukh Iron Ore Company Limited undertook planting of native species in large-sized pits of one cubic metre, but the species did not thrive. Among other things, availability of moisture during dry months was the limiting factor.

In our afforestation efforts during late 1980s and early 1990s, we mixed several species like mango, khair, heddi, kalam, bamboo, sandalwood, casuarina etc, sometimes to the extent of 50%. Although some of these species showed initial promise, later they had heavy failures compared to Acacia.

Acacia leaves and bark are used as fuel, leaves are also used as manure; wood is used as fuel and timber. Nearly 90% furniture sold in Malnad and coastal areas and also elsewhere as teak, is of Acacia.

In coastal areas, the floor under Acacia plantations was being swept to collect leaves and twigs for fuel. In areca-growing areas, leaves are used for mulching the areca plantations. Planters feel that the leaves disintegrate slowly, which is desirable. Acacia is planted by people along the periphery of their lands. In Shivamogga and Sagar towns, Acacia bark is sold as fuel.

Another Acacia by name Acacia mangium was being touted as Australian teak, and seedlings were being sold, with advertisements in newspapers, promising big profits in 10 years’ time. The author has seen the debacle caused by this species in Malaysia, where the species was banned.

During early 1990s, on the suggestion from the Karnataka Forest Department, the United Nations Educational, Scientific and Cultural Organisation and the Institute of Hydrology Roorkee (regional office at Belagavi), central organisation, undertook a study to find out the relative efficacy of Acacia plantations on water retention and its release later on. It was revealed that the Acacia plantations are not as good as natural forests, or the coffee plantations, but they are better than the open grass lands.

(The writer is former Principal Chief Conservator of Forests, Karnataka)