Status review of Rocky plateaus in the northern Western Ghats and Konkan region of Maharashtra, India with recommendations for conservation and management
34/6, Gulawani Maharaj Road, Pune, Maharashtra 411004, India
Abstract: Rocky plateaus in the northern Western Ghats and Konkan region are specialized habitats belonging to the general habitat category of Rock Outcrops. Their distribution and classification is presented here, with details of microclimate and edaphic features. Microhabitats on the rocky plateaus have been described along with characteristic species assemblages and changes in them due to biotic pressure. Ecological assessment of representative sites showhigh species richness and diversity (H’). A review of current knowledge about endemic flora and fauna on the rocky plateaus shows a large number of endemic species of flora and fauna, of which many are regionally assessed as threatened. Localized diversification within floral and faunal genera is common and indicates active speciation. Most localities except those within protected areas are affected by biotic pressures and there is no specific legal protection for their rich biodiversity. The paper suggests needs for future research on the habitat and recommends conservation and management actions based upon the ecology of the habitat.
Keywords: Biodiversity, endemic, ferricrete, Konkan, mesa, new taxa, northern Western Ghats, rocky plateaus, threats.
The Western Ghats are an imposing north-south range of hills that form the western edge of the Deccan Plateau and the narrow strip of land that lies between them and the sea is known as the “Konkan-Malabar region”. Western Maharashtra is composed of tall steep hills forming the northern part of the Western Ghats (henceforth referred to as NW Ghats) and the Konkan plains, which are interspersed with scattered low hills. The flat table-topped hills of the NW Ghats rise steeply to the east of the gently undulating plains of the Konkan. The present topography has resulted from intense physical and chemical weathering of basalt flows which in many areas has exposed duricrusts with scarce soil cover. Topographic maps of the region often mark these areas as “rocky scrub” or “stony waste” or simply as “sheet rock”. Owing to the scarcity of woody species or forest cover the plateaus appear devoid of vegetation in remote sensing images. Wastelands Atlas of India by the National Remote Sensing Centre and Ministry of Rural Development (2010) shows extensive “Category 22” (barren rocky /stony waste areas) in Kolhapur, Pune, Satara, Ratnagiri and Sindhudurg districts, which in reality are rocky plateaus with high biodiversity value. The wasteland status has been easily exploited for acquiring rocky plateaus for mining, wind farms and infrastructure projects throughout the study area. Owing to this, only a small fraction of the rocky plateaus remain undisturbed, mostly in the protected areas or inaccessible areas.
This paper reviews previous knowledge on the physical and biological environment of the rocky plateaus in the Western Ghats and Konkan region of Maharashtra. Based on detailed primary and secondary qualitative observations and quantitative assessments it discusses the diversity of organisms occurring on this specific habitat. Current biotic pressures and disturbance to the sites are documented, and conservation and management actions are suggested.
Distribution and classification of rocky plateaus in study area
The Western Ghats mountain range stretches from Navapur on the Gujarat-Maharashtra border to Kerala and is almost continuous with the exception of a gap near Palakkad. It thus traverses different bioclimatic zones and has a pronounced south-north gradient of increasing dry period length. The northern Western Ghats (NW Ghats) and Konkan differ in geology and bioclimate from the southern Western Ghats (SW Ghats) and the Malabar region. Jog et al. (2002) have described the general geology and geomorphology of the NW Ghats and Konkan. The crest of the NW Ghats is on average 1000m, but reaches up to 1400m in some areas (e.g., Mahabaleshwar).
The NW Ghats and the Konkan lie approximately between 15060’ & 20075’N and are composed entirely of Deccan flood basalts, except in the southernmost tip of the Konkan. Basalt is an igneous rock formed from the cooling of the Deccan Trap lava flows, which forms the base rock of the western part of Maharashtra State. The Deccan Traps are mostly arranged in flat layers giving rise to the flat plains of the Deccan and the layered aspect characteristic of the Western Ghats hills in Maharashtra.
The basalt has weathered to laterite on the hill tops but the laterite cover has eroded in most places and remains only as caps on the summits of the Western Ghats escarpment, especially south of 18020’N (Widdowson & Cox 1996). Laterite is a product of intense chemical weathering in a leaching environment and subsequent or simultaneous induration (Jog et al. 2002). Laterite can be found just below the ground as a hard, pavement-like surface which weathers by action of water courses, leaving the laterite as a resistant cap on upland mesas and plateaus, e.g., on Western Ghats hill tops. Laterites have also formed on the Deccan Traps along the plains of the Konkan coast, to which weathered laterite material from the Western Ghats ranges is added.
North of 18020’N (roughly Mahabaleshwar area) the lateritic cap has weathered away and the underlying basalt is exposed on the summits in the form of basaltic plateaus. Details of origin, evolution and geomorphology of these regions are discussed in Gunnell & Radhakrishna (2001) and Jog et al. (2002). Many of the plateaus in this region have undergone heavy weathering and have well-formed soil layers which support woody or forest growth. Forested plateaus like Mahabaleshwar or Bhimashankar have been discussed by Puri & Mahajan (1960), Pascal (1988), and Ghate et al. (1997). However, this work primarily deals with the exposed outcroppings of laterite and basalt in the form of rocky plateaus as they show many special features of floral and faunal communities.
The broad term, ‘rock outcrop’ has been used for landforms ranging from cliffs, isolated rocky hills, inselbergs (Porembski & Barthlott 2000), ferricretes and other rocky exposures of varying geological history. Wiser & White (1999) identified rock outcrops by prevalence of bare or lichen-encrusted bedrock that separates them from adjacent habitats; with on average 55% ground surface of exposed rock, while Porembski & Barthlott (2000) have emphasized upon the “naturally formed” or “primary outcrops” which are exposed due to geological reasons such as volcanism, weathering etc. The exposure of large rock surface leads to special microclimatic conditions such as high exposure to sun, shallow soils, water stress or excess etc., which in turn influences the prevalent plant communities. This leads to many similarities in terms of community assemblages and adaptive strategies of mainly flora and to a certain extent fauna associated with these habitats. The rocky plateau biodiversity described here, on ferricretes as well as basalt plateaus, is ecologically related to that on the other types of rock outcrops across the world due to these similarities in microclimatic conditions. The rocky plateaus are categorized on the basis of the rock type and geomorphology into two main types, each further divided by altitude into two:
A. Ferricretes - are indurated platforms of laterite typically with wide and flat to gently sloping flat tops and edges marked by sharp cliffs. Most floristic literature of the region refers to these as “lateritic plateaus”, without making clear distinction between the rocky lateritic plateaus and lateritic soil-covered plateaus. The map by Widdowson & Cox (1996) clearly shows the distribution of ferricretes in the western Maharashtra. They can be differentiated into:
A1. High-level Ferricretes (HLF) (Image 1) occur on High-Level Laterites between 15–18020’N, extend inland to 740E, and are located between 800 and 1400m (Widdowson & Cox 1996) in the districts of Satara, Kolhapur, Sangli, Ratnagiri, and Sindhudurg, which include the crestline of the NW Ghats. These also occur till the Belgaum District (Karnataka State), but not seen further southwards.
A2. Low-level Ferricretes (LLF) (Image 2) occur in the Low-level Laterites of Konkan plains between 50–200 m south of 18020’N in the Raigad, Ratnagiri and Sindhudurg districts, as well as all of Karnataka and the Kerala coast, extending from the sea coast to the foothills of the Western Ghats (see map by Gunnell 2001). They are much more extensively preserved than the high level laterites.
Ferricretes are often known as “tablelands” owing to the wide flat appearance and steep edges. In Maharashtra and Goa region they are known as “Sadas” in the local Marathi language. But the same term is also commonly applied to secondary exposures of laterites along hill slopes. (Image 4).
B. Basalt Mesa - The basalt outcrops are exposed on mesas between 18020’–210N & 73035’–73050’E (Image 3). These are areas where the upper layers of laterite have eroded to expose the underlying basalt flows, and hence can occur at any altitude depending upon the degree of weathering. Many of the hill forts of Maharashtra State have exposed hilltops of basalt. However, flora and fauna of basalt mesas (BM) at altitudes of 900–1100 m, especially at the crest of the NW Ghats, have many similarities with those of high-level ferricretes. These occur in Pune, Akole, Ahmednagar and Nashik districts. Very often they are known as “katal” in Marathi. In the Bhimashankar area of Maharashtra the term “kharam” lands was mentioned to indicate basalt outcrops and scree on gentle slopes. These are areas deemed unsuitable for agriculture by local people. Fig. 1 shows the study area with localities studied for this review.
Low-level outcrops of basalt are known to occur in Thane and Mumbai areas (Kanheri Caves), but they have not been surveyed in detail and hence are not discussed in this paper.
Review of literature
Rock outcrops of Africa, the Americas and Australia have been extensively studied for more than three decades. The distinctness of rock outcrops from surrounding habitats is a major factor whichleads to exclusivity of the plant diversity on them. Hence they have been described as “terrestrial habitat islands” and the microhabitats on them as “islands upon islands” (Porembski et al. 2000a). Azonal vegetation on tropical inselbergs in Africa, Australia and America has been studied by several researchers such as Burbanck & Platte (1964), Wyatt (1997), Porembski & Barthlott (2000b), and Burke(2003). But there is in general a scarcity of information regarding rock outcrop habitats of India. Globally, inselbergs of granite, sandstones, schists etc. have been studied in detail, but the same is not true for ferricretes and mesas. Ferricretes are known to be rich in species diversity, endemics and edaphic specialists (Verboom & Pate 2001), but only a few studies describe their vegetation (Porembski et al. 1994, 1997; Porembski & Watve 2005).
The only detailed information available on the distribution of ferricretes and mesas of the study area is from the geomorphological and geological literature. Geological Survey of India has published data on bauxite deposits of Maharashtra ferricretes. However, data on floristic and faunistic diversity remains scarce and widely scattered.
Bharucha & Ansari (1963) were the first to analyze the herbaceous vegetation of slopes and scree of Western Ghats in relation to soil, slope and aspect. Chavan et al. (1973) studied the Kas Plateau area (Satara District) but the study also includes cliff, forest and slopes around the Kas ferricrete. Regional floristic studies have reported the occurrence of many narrow-niched endemic and habitat specialist angiosperms from lateritic plateaus (Bachulkar 1983; Deshpande et al. 1993, 1995; Yadav & Sardesai 2002). Mishra & Singh (2001) have documented threatened plants of Maharashtra, of which many are reported exclusively from ferricretes or basalt outcrops. The first detailed enumeration of endemics from Goa by Joshi & Janarthanam (2004) includes many species specific to lateritic plateaus. The most recent study on floristics of lateritic plateaus by Lekhak & Yadav (2012) analyses angiosperm diversity in 10 sites of high level ferricretes.
Ecological studies and floristic and faunal observations on basalt and laterite outcrops have been published by Watve (2003a,b, 2006, 2007, 2008), and Watve & Thakur(2006). A review paper on the biodiversity and ecology of rocky plateaus (Watve 2010) has been included as a part of the Western Ghats Ecology Expert Panel (WGEEP) report on ecologically sensitive areas of the Western Ghats.
In spite of these studies there is little awareness at policy level regarding the special nature of rocky plateau biodiversity, and their conservation requirements need to be emphasized. Within the last decade many rocky plateaus have been taken over by mining, windfarms, construction of townships and industries. Tourism has been growing in some of the scenic areas putting severe pressure on fragile habitats. The management of these pressures is often misguided due to poor understanding about the special ecological features of the habitat. The measures used for protection of forest or grassland habitats are not appropriate, as the ecological processes on rocky plateaus are different in nature. The lack of baseline information regarding rocky plateau ecology has severely hampered efforts of management and conservation. Thus this is an effort to collate baseline information with a view to highlight conservation and management priorities.
The distribution of rocky plateaus in Maharashtra was mapped using extensive geological literature (Gunnell & Radhakrishna 2001; Didee et al. 2002). Topographic maps published by the Survey of India and mineral maps published by Geological Survey of India were screened to identify possible occurrences. Primary observational information from mountaineering, trekking literature was also screened. Records of bauxite deposits which indicate the distribution of ferricretes were also surveyed. Remote Sensing data was screened wherever available (Watve 2007), however it does not always provide a reliable record as many other non-forested or degraded areas look similar to the rocky plateaus in RS imagery. Rigorous ground-truthing was conducted between 2001–2012and field information was documented regarding disturbance status (qualitatively ranked low, moderate, high) and current threats.
Floristic, faunal and ecological information about the rocky plateaus have been collected from primary observations since 2001 and also from published literature.
Plant communities on six representative sites (two sites of high-level ferricretes each in Kolhapur District and Satara District and two basalt mesas in Pune District) were quantitatively studied and monitored between 2004–2006. At each site, five transects were laid down, at a distance of about 300m. Five permanent quadrats of 1x1 m were marked per transect at distance of 10m each. A total of 145 quadrats were monitored over three years to document seasonal variation in plant species composition and richness. Physical and chemical properties of the soil of ephemeral flush vegetation and shallow depressions were analyzed from eight NW Ghats plateau localities.
Regional floristic literature listing endemic species (Sharma et al. 1996; Singh & Karthikyan 2000; Tetali et al. 2000; Singh et al. 2001) was screened, for understanding endemism. Ecological data from protologues, primary observational papers and enumerations of endemic and threatened species was collated and habitat description was checked along with herbarium specimen data from BSI and AMH. Based on these, endemic species of angiosperms and pteridophytes reported to occur on the known rocky plateau localities were listed.
Checklists and description records of fauna were screened to identify species whichprimarily inhabit rocky plateaus. Primary and secondary observations from zoologists were used to identify species specific to rocky plateau habitats.
Results and Discussion
A total of 67 locations are described in the Table 1, grouped in the four rocky plateau types. Their exact locations are not mentioned due to high sensitivity of the habitats and species. Watve (2007, 2010) has reported climatic and microclimatic (soil, rock, air, temperature and humidity) conditions on rocky plateau sites. Insolation and scarcity of soil cause the microclimate on the plateaus to be more extreme than the surroundings. Seasonal variation in microclimate strongly influences the plant communities (Watve 2007). Diurnal variation is also extreme, as can be seen from Figs 2a–d. During the dry period, the thin soil layer does not hold any moisture and the conditions are almost arid. However, in monsoon, the impermeable nature of the hard rock surface leads to waterlogging of the soil and creation of ephemeral wetlands. As seen from this, the microenvironment of the rocky plateaus tends to extremes, from xeric to water logged.
Table 2 shows that soil varied from sandy to sandy loam type with good water holding capacity and normal EC. It was highly acidic (4.5–6), rich in organic carbon, available nitrogen and available potassium. Lekhak & Yadav (2012) relate the presence of carnivorous plants on the plateau to the poor nitrogen, phosphorous and potassium (N,P,K) values. However, the soil is poor only in available phosphorus. In addition to the carnivorous plants, many other plant species are able to survive in the habitat. Hence, the abundance of carnivorous species on rocky plateaus might be mainly because of reduced competition from other generalist species as a result of harsh physical environment, acidic soils and low levels of available phosphates. Presence and dominance of other plant adaptive strategies such as poikilohydry, geophytic, therophytic, hydrophytic species seen on rocky plateaus (Watve 2007, 2010; Lekhak & Yadav 2012) is also a result of extreme seasonality in climate as well as microclimate from seasonally wet to dry.
Description of microhabitats and vegetation (Images 5–10)
A standardized microhabitat classification has not yet been created for ferricretes or basalt plateaus. Plant species commonly seen in the microhabitats have been described by Watve (2003a, 2010) and Lekhak & Yadav (2012). These papers have used and adapted when necessary the microhabitat classifications used for ferricretes and inselbergs (Porembski et al. 1994, 1997, 2000a; Seine et al. 1998; Jacobi et al. 2007).
The ferricretes or basalt mesas in NW Ghats and Konkan, do not have microhabitats as clearly demarcated as on inselbergs. Due to the heavy monsoon, all depressions or flat surfaces and even boulders in depressions become waterlogged during the rains. Thus, there is much overlap seen between species in microhabitats. Some species are able to grow in closely similar microhabitats, e.g., Lekhak & Yadav (2012) describe Aponogeton satarensis as growing in SFD (Soil filled Depressions) as well as SEP (Small Ephemeral Pools). Utricularia albocaerulea, U. purpurascens, Eriocaulon sedgwickii or E. eurypeplonare not restricted to Ephemeral Flush Vegetation (EFV) on ferricretes, but also seen growing in shallow depressions (SD) with soil 10–20 cm deep. They are able to grow in a range of microhabitats, but in lesser dominance in areas where grasses, sedges and other ephemeral flora can compete with them due to soil availability. Very few species, with specific adaptation such as Nymphoides spp. and Wiesneria triandra are restricted to a single microhabitat (ponds or water pools). Most of the species are able to grow across a wide range of soil depths and slopes, although their dominance varies as per the specific habitat requirements.
The microhabitat classification described here is based on Seine et al. 1998 and Porembski et al. 2000a, with some modifications as in Watve 2010 (Table 3). However, this and all other microhabitat classifications are limited by the fact that on the rocky plateaus there is no clear physical demarcation between the habitats. An appropriate classification specifically for rocky plateaus can be finalized only after detailed ecological studies from diverse rocky plateaus in India.
The general vegetation is similar to ephemeral communities from granitic rock outcrops—Inselbergs and iron rich plateaus—in East and West Africa and Brazil (Porembski et al. 1994, 1997; Jacobi et al. 2007). Presence of Cyanotis, Neanotis, Murdannia, Drosera, Utricularia, Lindernia, Burmannia, Fimbristylis, Rhamphicarpa matches with that on paleotropical inselbergs described by Porembski & Brown (1995) and Dörrstock et al. (1996). Dominance of Rotala and Dopatrium in water-filled potholes is similar to the vegetation of seasonal rock pools described by Krieger et al. (2000). The presence of Ceropegia, Dipcadi, Aponogeton, Utricularia, Euphorbia corresponds to that of iron rich ferricretes of Rwanda and Zaïre described by Porembski et al. (1997). Insectivorous plants are a characteristic of African as well as Indian outcrops. Thus the overall vegetation has close affinities to the palaeotropical regions.
Herbaceous vegetation on six rocky plateau sites of the NW Ghats was monitored to document temporal changes in monsoonal diversity of six sites of high altitude plateaus. The sites Z,M,C,Kwere high level ferricretes (HLFs) and D,A were basalt mesas (BMs) (See Table 1 for details). A total of 145 quadrats were monitored for two years (2004–2005 on five sites and 2005–2006 on one site). The quadrats covered shallow depressions, seasonal rock pools, cryptogamic crust, boulders and ephemeral flush vegetation (EFV), thus representing the most common microhabitats on the NW Ghats plateaus. The data collected were analyzed to understand changes in species richness calculated as total species number (N) and diversity (H’- Shannon’s diversity index). Results are presented in Table 4 and Fig. 3a,b.
Early phase of monsoon (July) was period of vegetative growth of most species and very few species (Habenariaspp., Dipcadi spp.) started flowering in this period. Plants of Cyperaceae, Poaceae, Eriocaulaceae started emerging but were only distinguishable at morphospecies level. Hence quantitative data of this phase was not completely reliable. Late phase of monsoon corresponded roughly to August end or September first week, which was a period of characteristic mass blooming mainly of non-grass families (Fabaceae, Eriocaulaceae, Lentibulariaceae, Rubiaceae) observed on all rocky plateaus. Species richness as well as species diversity peaked at this period as most species of forbs and grasses completed their growth during this period. The species richness as well as diversity declined again in the post monsoon (October) when most forbs withered away after completing growth and grasses (Dimeria spp., Dichanthium spp. Ischaemum spp.) dominated vegetation and reached seed dispersal stage.
Only a very few annuals and perennials were seen in the winter and summer period and species richness as well as diversity were very low (3–4 species). Of the selected sites, highest species richness and diversity were seen on site D, a basalt mesa in Pune District.
From a total of 145 quadrats (area 145m2), 132 species were reported (Watve 2007) including 57endemic angiosperms. These included 126 angiosperms, three bryophytes (identified only as morphospecies) and three pteridophytes. Poaceae (36 sp.) and Fabaceae (14 sp.) were the most species-rich families in the microhabitats surveyed.
Lekhak & Yadav (2012) have reported more than 300 species from 10 sites. The number is likely to increase as more surveys are carried out. Rocky plateaus are not completely separated from surrounding habitats and some herbaceous species from scrub and forest, can grow in areas of deep soil adding to the species number.
Many species of cryptogams (green algae, blue green algae, lichens, liverworts) were seen on the rocky plateaus but were not identified to species level. G. Chitale (pers. comm. 2012) has documented saxicolous lichens in the study area, and has described many species from the rocky plateaus of Panchgani Tableland, Bhimashankar, Kas, Kolhapur and Junnar areas. A complete assessment of cryptogamic vegetation from diverse sites is required and will add valuable information about the biodiversity and nutrient cycling on these areas.
Detailed listing of fauna exclusively of rocky plateaus has not yet been carried out. However, diverse vertebrate and invertebrate taxa have been reported from microhabitats on plateaus. Unlike flora, faunal species have the ability to move away from outcrops in stressful conditions of summer or heavy monsoon and seasonal studies are required to assess the complete faunal diversity. Ground dwelling ants, beetles, spiders, scorpions, grasshoppers, odonata, ground nesting birds, reptiles; small and large mammals are often seen on rocky plateaus (Image 11–14). Raptors including migrant species like Lesser Kestrel (Thakur & Watve 2004) have been commonly seen on and around the rocky plateaus. Tadpole Srimp (Triops granarius Lucas), Fairy Shrimp (Streptocephalus dichotomus Baird), and Clam Shrimps (Leptestheriellaspp. Nayar & Nair) have been frequently observed in seasonal rock pools (H. Ghate pers. comm. 2012). Shrimps also show adaptation to extreme climate of rocky plateaus as their eggs remain dormant in ephemeral pond soil till the approach of the monsoon.
The smaller invertebrate fauna commonly use boulders on plateaus for shelter during extreme conditions, while the same are used by lizards such as Sitana ponteceriana for display. Malabar Crested Larks have been seen very commonly on the plateaus, foraging, displaying on boulders, and nesting. Frogs spawn in ephemeral pools. Lizards, geckos, skinks (Hemidactylusspp., Sitana ponticeriana, Cnemaspis spp.) and caecilians have been frequently observed on plateaus. However, most of the plateau fauna is not easily visible and often takes shelter under boulders especially during the day, either to avoid the harsh sun or because of vulnerability to predators like raptors (eagles are frequently noted) in the open areas. Laterite plateaus have deep caves beneath which are roosting sites for bats as on Panchgani Tableland and Robber’s Cave of Mahabaleshwar. Except some of the herpetofauna, endemism and threat status of fauna has not been critically assessed.
Conservation value of rocky plateaus
High endemism and recent records of many new species in diverse taxa from the rocky plateaus in the study area indicates high conservation significance.
Joshi & Janarthanam (2004) first described lateritic plateaus of Goa as habitats showing rich floral endemism. High endemism in rocky plateau vegetation of Maharashtra has been reported by Watve (2007, 2010) and Lekhak & Yadav (2012). A list of endemic species and varieties (as per the listing by Singh & Karthikeyan 2000) that occur on rocky plateaus has been compiled, based on floristic literature and personal observations from the region (Table 5). The threat status as per regional assessment made by Botanical Survey of India (Mishra & Singh 2001) and those completed as part of IUCN Freshwater Biodiversity Assessments are added. Mapping of distributional ranges of endemic herb species is not available for this region. Hence, it is not possible to identify species “exclusive” to the rocky plateaus. Many recently described plant species may have wider distribution than believed at present.
A detailed analysis of endemism on rocky plateaus can be carried out only after regional endemic lists are revised. Hence the list in the Table 5 should be treated only as an indicative one. So far, 188 endemics species have been recorded from primary and secondary observations on the rocky plateaus in the Western Ghats and the Konkan region. The list of endemics is likely to increase as more sites are surveyed. A large number of endemic species on the rocky plateaus are not exclusive, but widespread in similar open moist and sunny habitats such as stream courses, forest edges, cliffs, shrublands etc. However, it can still be safely concluded that the rocky plateaus do serve as important habitats for a large number of endemic plant species.
High endemism in substrate-specific communities is well known across the world (Mota et al. 2004; Chiarucci 2004; Stevanović et al. 2003; Ojeda et al. 2000; Keener 1983). Burke (2003) has shown that rock outcrops make significant contribution to the local and regional species richness. Von Gaisberg & Stierstorfer (2005) have shown a connection between distribution of endemics and geomorphological and geochronological traits of outcrops on El Hierro island in the Canary Islands archipelago. Endemism on outcrops is in many cases correlated with the regional endemism (Seine et al. 1998). This is also indicated in the present listing as Poaceae species number is highest in the list of endemics and the same is highest in generic endemism in India (Irwin & Narasimhan 2011).
Dimeria, Dichanthium, Glyphochloa, Eriocaulon, Utricularia and Smithia include many widely distributed species in the region, but have speciated into narrow endemics with restricted distribution on few rocky plateau localities, e.g., Dichanthium panchganiensis, Ceropegia jainii, Aponogeton satarensis seen on HLF. Such endemics with restricted distribution are more on high level plateaus as they are separated from each other by deeply weathered areas and function as terrestrial habitat islands especially for species with dispersal limitations. Shukla et al. (2002) have observed a similar manner of speciation in Isoetes on the high- altitude plateaus in the Western Ghats and central India. The Konkan ferricretes are more or less continuous without distinct breaks. Hence many endemics such asDimeria woodrowii are widespread in Konkan. However, Konkan plateaus are affected by landuse changes and other biotic pressures, which have caused fragmented populations of species such as Dipcadi concanense.
Mishra & Singh (2001) and Lekhak & Yadav (2012) have assessed many angiosperm endemics as Critically Endangered, Endangered, Vulnerable or Near Threatened using IUCN Red List Categories and Criteria Version 3.1 (IUCN, 2001), though a complete global assessment has not been made so far. This indicates urgent need of a threat assessment of the rocky plateau habitats to identify priorities for conservation of species.
During the IUCN Freshwater Biodiversity Assessment, (Molur et al. 2011), some species including Aponogeton satarensis, Eriocaulon tuberiferum, Wiesneria triandra,Utricularia spp. that occur in seasonal pools and EFV on rock outcrops were globally assessed, of which two were included in Critically Endangered, three in Endangered and three in Vulnerable category. Aponogeton satarensis, was assessed Endangered (IUCN 2011) based on restricted distribution and current threats. Widespread species such asWiesneria triandra, were assessed Least Concern (IUCN 2011), as they can easily colonize secondary habitats such as rice fields which have waterlogged conditions similar to its primary habitats.
In recent years, new species of Chlorophytum, Eriocaulon, Mnesithea, Isoetes, Rotala etc. have been described from rocky plateaus. Surveys of adjacent areas need to be conducted to record the distributional ranges of these species. Kruckberg (2002) had shown that local diversification of plant life is typical for landscapes dominated by geomorphological irregularities at a scale of 10-2-10km2. Thus even the smallest of the rocky plateaus are extremely significant for local plant diversity and need immediate protection.
The trend of high endemism and restricted distribution seen in plants, is also seen in case of fauna. Abundance of endemic Hemidactylus albofasciatus, (Grandison & Soman 1963; Gaikwad et al. 2009) on LLF, and caecilians Gegeneophis seshachari (Gower et al. 2007), Indotyphlus maharashtraensis from HLF (Giri et al. 2004), recent description of Hemidactylus satarensis(Giri & Bauer 2008) from Satara plateau and Xanthophryne tigrinusfrom Amboli region (Biju et al. 2009) indicates that local speciation on rocky plateaus is also seen in herpetofauna. It is also extremely necessary to take up listing and distribution studies of invertebrate fauna to analyze if similar trend is observed in other taxa.
Presence of endemic flora and fauna, presence of habitat specific plants as well as animals and many descriptions of new localized species clearly indicate a high conservation value for the habitat. The HLF, LLF and BM each have characteristic endemic plants and animals which are exclusive to them. Hence, conservation of representative areas of each type of rocky plateaus needs to be planned.
Humans and rocky plateaus
People form an integral part of most rock outcrop landscapes across the world. In the study area, local people have specific names such as “Sada” for lateritic plateau and “Katal” for basalt outcrops. The presence of temples on most rocky areas and associated legends indicate that these are well-known features in the landscape. Dhangars (=shepherds) of Satara District use the rocky plateau habitats for grazing of livestock. On Jagmin Plateau in Satara District local community has a practice of leaving boulders in mound at one place in memory of the dead. Every year on certain date a ritual is performed there and offerings placed. Many large plateaus have a temple of the local deity e.g. Masai, Mhavashi, Patan, Durgawadi rocky plateaus. Some of them are locally well known and attract large number of people at festival times.
Owing to the hard impermeable rock surface, rocky plateaus serve as water catchments. The lithomarge allows water drainage from underground channels and perennial springs are commonly seen along the plateaus. Mass blooming of the plants on the rocky plateaus offers abundant food supply for the pollinators, which is important for crops and orchards in surrounding area. It is necessary to further evaluate ecosystem services of the plateau such as nutrient cycling etc.
Impact of biotic pressures
The entire Western Ghats and Konkan region is under heavy biotic pressures and rocky plateaus are no exception. Grazing, trampling, conversion to agriculture, quarrying have been going on for several years. Agriculture, tourism, windmill farms, mining and more recent land use changes have taken a heavy toll on the rocky plateaus habitats.
(i) Grazing, trampling, fire: Grazing by cattle, trampling and fire are common on all plateaus easily accessible to people except in remote plateaus of Sahyadri Tiger Reserve. The plateaus are tolerant to low amount of grazing, as even wild herbivores such as hares,Barking Deer, Sambar and Gaur regularly graze on the plateaus. However, increase in grazing pressure can directly affect some sensitive biodiversity and further studies are required. Putting fire to the vegetation on plateaus is a regular feature on Kas and Zenda plateaus. It is not a natural phenomenon and mostly done by careless tourists and poachers. This causes destruction of fauna and affects seed banks in the shallow soil which are necessary for future growth of vegetation. It may affect the characteristic plant communities in future.
(ii) Agriculture, ponds and plantation: Agriculture on large scale is not possible on the rocky plateaus. However, in recent years, government schemes for reclamation of wastelands for cultivation have affected some plateau areas in Pune District. Schemes of water storage and water conservation, leading to digging of ponds, bunding, bund plantation of exotic trees have all caused many changes to the high- altitude plateau flora. Some plantations of bamboo and Acacia auriculiformis were made by the forest department on plateaus in Satara District. These species either do not survive or remain stunted owing to the harsh climate here. But trenching and digging for the plantations damages the natural microhabitats (Image 15).
Conversion of plateaus into mango orchards has led to the degradation of many rocky plateaus in Ratnagiri and Sindhudurg districts.
(iii) Quarrying: This has had the largest impact on the entire Konkan (low-level laterite) areas. The deep layers of laterite are extensively quarried and the bricks (= chira/jambha) used for construction locally, and increasingly in areas as far away as Pune and Mumbai. Quarrying is rampant and a major source of destruction of Konkan laterite (Image 16).
(iv) Wind farms: The rocky plateaus near Chalkewadi, Boposhi, Jagmin, Patan (all in the Satara District) are entirely taken up by windmill farms of high intensity (Image 17). The wind farms are present on private lands but are adjacent to the forest lands of Koyna and Chandoli Wildlife Sanctuary within Sahyadri TR. The presence of windmills has led to construction of roads and buildings which now divide the large plateau into many sectors. The rubble of the construction is thrown on the plateau. The digging and construction have disturbed the drainage pattern on the outcrops leading to disturbance of natural microhabitats. Increased disturbance encourages entry of invasive species, exotic as well as indigenous, from surrounding scrub areas, which can colonize the new habitats. Senecio bombayensis and Blumea oxyodonta, species which belong to the scrub areas and are thus alien to the plateau microhabitats, are now seen growing on rubble heaps between the windmills and along the roads.
Although the number of localities showing windfarms is small, some of the largest plateaus at high altitude, Chalkewadi and Mhavashi, Boposhi are entirely taken up by windfarms. Many new areas are proposed for development, even at the cost of RF lands. Pande et al. (2013) have assessed bird collision risk in a windfarm and recommended that EIA should be made mandatory for windfarms in Western Ghats.
(v) Tourism: Heavy tourism has destroyed the natural diversity of Panchgani Tableland and the same threat is posed to the Kas Plateau, recently declared as World Heritage Site. The destructive activities on Panchgani Tableland such as horse riding, vehicle driving have been banned by the High Court. Although this tableland is part of Mahabaleshwar-Panchgani Ecosensitive Zone and a declared conservation zone and natural heritage site, its biodiversity has not received any special protection. Kas is an area of reserved forest, where forest department is trying to regulate tourism in an effort to make it sustainable. However, one needs to first study tourist carrying capacity and tourism impact on such sensitive habitats (Image 18).
(vi) Mining: Mining is the most harmful of anthropogenic activities on the rocky plateaus. High level lateritic plateaus have deposits of aluminium ore bauxite underneath the hard surface. Lad & Samant (2009) have documented the environmental and social impacts of mining in region. The Kolhapur plateaus are well known for high quality bauxite and many have been mined for more than 20 years. At present, only the rocky plateaus within the Sahyadri TR are protected from bauxite mining.
(vii) Developmental projects: Of the diverse rocky plateaus studied, those in Konkan (LLF) are at most risk, as none of them falls under any legal protected area. These vast and biologically rich plateaus have been claimed for nuclear power plant, conversion of land into intensive urbanization and industrialization. The land conversion is very easy because the rocky plateaus fall under ‘wasteland’ category. Jaitapur nuclear power plant, Ratnagiri airport, Ratnagiri MIDC, Devrukh townshipare some examples of development on Konkan plateaus. The sad neglect of such a specialized habitat and its biodiversity needs to be stopped immediately.
(viii) Invasive species: The species that grow on rocky plateaus are adapted to the extreme physico-chemical and climatic conditions of this habitat and have a competitive advantage over other species of more mesic environments. However, activities that disturb the sensitive balance lead to invasion by generalists from surrounding, either indigenous or non-indigenous, species. This is already seen on some rocky plateaus whichhave been exposed to prolonged disturbance such as Panchgani Tableland. Building a road, digging pits for windmills, plantation lead to soil upheaval. Debris dumping allows establishment of Seneciospp. Heteropogon contortus, Cynodon dactylon from surrounding scrub grassland. On some plateaus, around ponds, hardy weeds such as Argemone mexicana have established. Influx of tourists on large scale has led to accidental intrusion of invasives from faraway areas, garden weeds (Tridax procumbens, Synedrella nodiflora etc.) on the Panchgani Plateau. Invasives compete with the specialist vegetation of similar herbaceous nature. This is one of the most serious threats to the special biodiversity.
The impacts discussed above indicate the nature and diversity of threats to the rocky plateaus in study area. Immediate steps need to be taken for conservation and management.
As seen from the discussion above, most rocky plateau sites are facing threats except those in protected areas. Thus only a limited spectrum of biodiversity of the lateritic plateaus is under legal protection. It is necessary to take immediate conservation action to protect less disturbed rocky plateaus representative of the three types (LLF, HLF and BM) and also for specific rare and threatened species.
The biotic pressure varies from low impact with slow degeneration of species population such as by trampling to high impact with total destruction of the habitat and its diversity as in case of mining.
As emphasized above in the discussion, many more exploratory and experimental scientific studies are required to aid the conservation planning. However, the processes such as land conversion are happening at such a fast rate that scientific studies may not be completed before the decisions of conversion are made. Hence, in addition to the scientific studies, simultaneous actions for conserving known sites of high diversity are necessary.
Suggested conservation actions are:
A. Conservation of habitat: Areas of high conservation significance which are currently under threat need to be identified and immediate measures have to be taken for conservation of the habitat. CEPF-ATREE funded small grant project “Networking and Information Support for Rocky Plateau Conservation in Sahyadri-Konkan corridor” was initiated based on this view. It attempts to identify and strengthen ongoing conservation and restoration projects on 15 rocky plateau sites across the NW Ghats. The aim is to link scientific documentation with conservation planning, which will ultimately help in protecting the sites.
B. Conservation of species: Another approach is to identify areas occupied by highly threatened taxa or those with restricted distribution and accord legal protection for in situ conservation of the species. At present the threatened species of plants and animals and their habitats are not protected under any special legal status. Thus it is impossible to take legal action against destruction of habitats or populations of threatened species.
All the available scientific data indicates that the rocky plateaus function as terrestrial habitat islands. Therefore it is necessary to protect a large number of sites throughout the distributional range of the habitat if a significant percentage of rock outcrop biodiversity is to be protected. It will be impossible to include all or even a few in a single protected area. However, considering the importance of the habitat, as many sites as possible need to be protected.
Some specific suggestions are:
1. For rocky plateaus under ownership of forest department
- Extra protection to be given against mining or conversion to wind farms, grazing, fires, heavy tourism, and monitoring for indirect threats.
- Managing the plateaus in Reserve Forest and ecosensitive areas for conservation of biodiversity and ecology. Regulation of landscape changes such as plantations, construction of bunds, ponds, tourism, by scientific methods. Involving local communities in conservation, monitoring, sensitization towards ecosystem services.
- Additional protection to surrounding private lands to help in conservation.
2. For rocky plateaus not under the ownership of forest department
- Identify level of protection required. Sanctuary notification is very difficult at present if they are not already forest lands. Acquiring of revenue, private lands, designation of other conservation categories such as conservation zones can be considered and management guidelines can be formed for appropriate protection.
- Discouraging quarrying, mining, power plants by conducting thorough impact assessments and declaring the areas biodiversity rich and hence “no-go” for large scaledevelopment.
- Assess feasibility of cluster sanctuary especially for the Konkan plateaus, which have residual patches due to fragmentation of habitats.
3. Create awareness and build capacity at all levels
- For scientists, who can contribute towards scientific understanding of the habitat,
- For society, for monitoring the habitats, forming pressure group for conservation, responsible tourism,
- For local community, for local management, conservation benefit sharing, reducing impacts by providing alternative housing material, controlled grazing, controlled agriculture,
- For Policy makers, for developing specific policy recommendations for better protection of the rocky plateaus and also of other rock outcrops.
The nature of biodiversity of the rocky plateaus and the habitat is different from forest or grassland habitats. The biodiversity of the rocky plateaus has evolved and specially adapted to phosphate poor azonal soils with seasonal extremes of water availability. These conditions are formed as a result of natural processes of weathering over millions of years. The nutrients and water need to continuously seep through the different habitats, maintaining a flow of nutrients across the microhabitats for allowing the natural plant and dependent animal communities to develop. Introducing artificial blockages in the flow of nutrients and water will result in altering the ecosystem processes (Image 14) and ultimately change the vegetation, by allowing easy establishment of grasses, shrubs and trees from surrounding scrub areas such that it will eventually compete with the specialized endemic flora. Hence, it is necessary to understand that typical habitat management practices such as soil and water conservation should not be practiced for this habitat.
Fire is not a natural part of this habitat, and leads to burning of already scarce biomass, lichen and moss flora important in nutrient fixing and alters the ecosystem at the same time affecting fauna. Hence, it should be prevented. Although grazing by domestic cattle on low scale does not appear to be harmful to the habitat, studies are required to see to what extent it can be allowed at each site, as the cattle competes with the wild herbivores.
Removal of plants and animals species, natural to the habitat should be prohibited. To protect diverse plant communities, care should be taken to maintain the entire range of microhabitats described in this paper. Removal of boulders, filling of shallow ponds, or altering the drainage pattern can have severe impacts on biodiversity which may be visible only after some years.
Tourism, wind farms, infrastructure development and mining are serious threats to the rocky plateaus. Unfortunately, ecological impact assessment (EIA) is not mandatory except for mining in the region. But considering the sensitive nature of the biodiversity of the rocky plateaus, comprehensive EIA should be made mandatory for any development affecting the area which should include extensive studies in monsoon season.
Following recommendations can be made based on above:
- Exclusion from the wasteland or Barren Rock Category
- Scientific enumeration of the floral and faunal richness of the habitat including those in the PAs as well as non PAs with special focus on lesser-known cryptogamic vegetation and invertebrate fauna
- Exploring plant-animal relationships on rocky plateaus (e.g., pollination)
- Global threat assessment of the endemic elements as well as other species at local level. Compilation of distributional data of endemic herb species for understanding their dependence on rocky plateau localities.
- Establishment of experimental research projects to understand rocky plateau ecology, ecosystem processes, services, and linkages
- Monitoring the rocky plateau ecology on long-term basis
- Assessment of ecological status of the rocky plateaus and biodiversity
- Enhanced protection of rocky plateaus within existing protected areas and protection of additional representative sites to complement currently protected sites
- Involving local communities in conservation and monitoring exercises
- Limiting destructive activities such as mining, plantation, tourism, constructions and burning on plateaus
- Awareness generation about the importance of preserving these habitats in scientists, policy makers and society
It is hoped that this approach will prove to be a step towards a much more comprehensive study of the biodiversity of rock outcrops in entire India and will sensitize policy makers to design conservation strategies for this unique habitat type.
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