R. J. Ranjit Daniels

Impact of Human Extraction on Tropical Humid Forests in the Western Ghats Uttara Kannada, South India

1. Thirty strip transects of 2400 m 2 each, in the evergreen forest tract of the district of Uttara Kannada in South India, were clustered into two groups with high and low levels of disturbance on the basis of the density of perennial flowering plants and the fraction of deciduous species. 2. The set of 20 transects corresponding to low disturbance localities harboured 48 ± 6 (mean ± SD) species and 694 ± 135 individuals per transect, while the other 10 transects affected by high levels of disturbance supported 36 ± 12 species and 379 ± 135 individuals. 3. Eighty-four of the total of 200 species (operational taxonomic units) were exclusive to sites of low disturbance, and 28 to those of high disturbance ; 88 species were shared by sites of high and low disturbance. This number of shared species was significantly less than expected on the basis of chance alone. 4. The differences in species richness, as well as those in species turnover (0.73 ± 0.07 for high and 0.65 ± 0.01 for low disturbance sites) were significant at the 1 % level, but were as expected given the lower plant densities at sites of high disturbance. 5. Lack of coppicing ability in conjunction with their use in the plywood/matchwood industry has led to the disappearance of several evergreen species such as Syzigium gardneri and Myristica malabarica at sites with high levels of disturbance. 6. With villagers concentrating on harvests of trees in the height class of 4-8 m as poles, and commercial interests mostly extracting trees > 16 m in height, there was a reduction of around 45% across all height classes between sites of low and high levels of disturbance.

Birds of the man-made ecosystems: the plantations

One-hectare plots were sampled for bird species diversity in the Uttara Kannada district. These plots represented well-preserved evergreen/semievergreen forests, secondary/moist deciduous forests showing different levels of degradation by man and plantations of teak, eucalypts and betelnut. It was found that the betelnut plantation and the evergreen/semievergreen forests had the least bird species diversity ofH′ = 2.58 and 2.61 respectively. The eucalypt and teak plantations hadH′ = 2.69 and 2-92 respectively. In the secondary/moist deciduous forests it ranged from 2.80–3.39. Despite the apparent increase in diversity in the man-modified vegetation types, it was found that there was a gradual displacement of the bird species composition from what was typical to the evergreen forests to those of more urban and scrubby habitats in these man-modified vegetation types. This was particularly so in the eucalypt plantation.

Changes in the bird fauna of Uttara Kannada, India, in relation to changes in land use over the past century

The hilly district of Uttara Kannada (13° 55′ N–15° 32′ N Latitude and 74° 5′ E–75° 5′ E Longitude), with an area of 10 200 km2, is one of the most forested tracts of south India, although the total area under forest has been reduced from 80% to 70% over the past century. Excellent documentation of the bird fauna exists from the 1890s and 1980s, with a shorter survey conducted in 1938. An analysis of these three surveys suggests that the size of the total bird fauna has remained constant around 465 ± 20 taxa over this period. However, most of the thirty-one resident bird taxa recorded earlier but not sighted in the recent survey, as well as nine taxa observed only recently, are notable habitat specialists. Only a few of these specialists that have probably been lost over this period are forest birds, the majority being characteristic of the drier cultivation and scrub areas. Recent invaders seem to prefer aquatic ecosystems, and it is suggested that this may be a more general pattern. It is therefore vital that more attention be paid to conservation of the biological diversity of the semi-arid tracts of the Indian subcontinent.

A strategy for conserving the biodiversity of the Uttara Kannada district in South India

Taking the various values ascribed to biodiversity as its point of departure rather many years ago, the present study aims at deriving a conservation strategy for Uttara Kannada. This hilly district, with the highest proportion of its area under forests in South India, is divided into five ecological zones: coastal, northern evergreen, southern evergreen, moist deciduous, and dry deciduous. The heavily-populated coastal zone includes mangrove forests and estuarine wetlands. The evergreen forests are particularly rich in the diversity of plant species which they support - including wild relatives of a number of cultivated plants. They also serve a vital function in watershed conservation. The moist deciduous forests are rich in bird species; both moist and dry deciduous forests include a number of freshwater ponds and lakes that support a high diversity of aquatic birds. Reviewing the overall distribution of biodiversity, we identify specific localities - including estuaries, evergreen forests, and moist deciduous forests - which should be set aside as Nature reserves. These larger reserves must be complemented by a network of traditionally-protected sacred groves and sacred trees that are distributed throughout the district and that protect today, for instance, the finest surviving stand of dipterocarp trees. We also spell out the necessary policy-changes in overall development strategy that should stem the ongoing decimation of biodiversity. These include (1) revitalizing community-based systems of sustainable management of village forests and protection of sacred groves and trees; (2) reorienting the usage-pattern of reserve forests from production of a limited variety of timber and softwood species for industrial consumers, to production of a larger diversity of non-wood forest produce of commercial value to support the rural economy; (3) utilizing marginal lands under private ownership for generating industrial wood supplies; and (4) provision of incentives for in situ maintenance of land-races of cultivated plants - especially evergreen, fruit-yielding trees - by the local people. It is proposed that this broad framework be now taken to the local communities, and that an action-plan be developed on the basis of inputs provided - and initiatives taken - by them.

A landscape approach to conservation of birds

Landscape ecology as a discipline in science is rather young. However its principles appear promising in outlining conservation strategies including a wide range of organisms, particularly birds. Birds due to their mobility use a variety of environmental resources, especially habitats. However, currently these habitats are only available in patches over most of the tropical world. Further whatever is left is under constant human pressure. This paper, therefore, addresses this problem and suggests means of dealing with it using the landscape approach as outlined by landscape ecology.The landscape approach starts with the realization that patches of habitats are open and interact with one another. Corridors of trees along roads, hedgerows and canals in a landscape can aid in the movement of species. Hence the landscape approach considers patches of habitats as interacting elements in the large matrix of the landscape. The landscape approach also integrates concepts. It puts together often debated issues such as whether to preserve maximum species diversity, to maximize representativeness, or to preserve only the valuable species. Based on a case study of the Uttara Kannada district in Karnataka, these oft-opposing views and complications can be dealt with practically and synthesized into a conservation strategy for the diverse avifauna of the Western Ghats.

Reply to Sridhar: Agricultural landscapes remain an essential front for biodiversity conservation

Sridhar asserts that more data are required to claim conservation benefits for arecanut cultivation (1). More research might be useful, but our data amply support our conclusions (2). Sridhar suggests that the forest bird species in arecanut plantations were strays from nearby forest. But why was that forest there in the first place? In general, long-term human use … 2To whom correspondence may be addressed. E-mail: jai.ranganathan{at}gmail.com or pre{at}stanford.edu