Technical Reports
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Item Study on Ecological & Socio-Economic Impact of Invasive species, Prosopis juliflora and Lantana camera and their removal from forest, common and fallow land of Tamilnadu(Wildlife Institute of India, Dehradun, 2018) Sivakumar, K.; Rawat, G.S.; Badola, Ruchi; Adhikari, B.S.; Kamalakannan, B.Item Study on ecological and socio-economic impact of invasive species, Prosopis juliflora and Lantana camara and their removal from forest, common and fallow land of Tamilnadu(Wildlife Institute of India, Dehradun, 2018) Sivakumar, K.; Rawat, G.S.; Badola, Ruchi; Adhikari, B.S.; Kamalakannan1) Prosopis juliflora is an invasive, drought resistant, evergreen fast growing pheratophyte widely distributed in India and also in arid and semi-arid tropical countries. It is a highly valued wood source for rural people in India. The P. juliflora is believed one of the worst invaders affecting natural and man-made ecosystems and its local biodiversity in Tamil Nadu. In this context, this study was conducted aimed to assess the distribution patterns of P. juliflora and its impacts in three different agro-climatic zones of Tamil Nadu. 2) In 1959, Prosopis juliflora was introduced in Tamil Nadu to meet the fuelwood requirements of the rural poor people and to re-vegetate the degraded lands but it spread at faster and occupied almost all agro-zones of Tamil Nadu. In India, P. juliflora was considered as one of the worst invaders in the country affecting natural ecosystems and local biodiversity. In order to eradicate this species from natural forests, preparation of a restoration plan is desirable with knowledge on ecology and impacts of P. juliflora in Tamil Nadu. Keeping this in view, Wildlife Institute of India with support of Tamil Nadu Forest Department assessed the extent and abundance of P. juliflora in forest, common and fallow land of Tamil Nadu. Initially, the study was started in the southern zone of Tamil Nadu and later in other agro-climatic zones of Tamil Nadu (i.e. Cauvery delta zone (Nagapattinam district), Southern zone (Ramanathapuram district) and Western zone (Sathiyamangalam Tiger Reserve, Erode district). 3) Totally ninety transects were laid randomly in three agro-climatic zones of Tamil Nadu. Each transect of 2 km length, it had six 15 m radius plots at equal distance of 400 m to quantify the environmental parameters such as vegetation structure and composition, cover percentage of grass, native herbs, weeds, animal pellet and bird abundance, etc., was recorded by using standard methods on the same transect. Influence and impact of Prosopis juliflora and its and socio-economic status were assessed by using a questionnaire survey in entire taluks of three agro-climatic zones. 4) The results revealed that occupancy of Prosopis juliflora was more in the southern zone compared to the other two zones. Southern zone occupies 79.4% of Prosopis juliflora invaded in this region than western zone (46%), and in Cauvery delta zone (32%). Density (F = 34.35, P < 0.05) and frequency occurrence (%) of P. juliflora were also higher in the southern zone followed by western zone and Cauvery delta zone. The richness and native biodiversity of plants and related herbs, shrubs were highly ruined in southern zone followed by Cauvery delta and western zone. The highest extent of Prosopis was observed in the entire seven taluks of the Ramanathapuram district (southern zone) compare to the Nagapattinam taluks (Cauvery delta zone) and Sathyamangalam Tiger Reserve ranges (western zone). Except Prosopis juliflora and Lantana camara; Parthenium hysterophorus and 2 Chromolaena odorata caused huge smash up to the native ecosystems in some ranges of Sathyamangalam Tiger Reserves. 5) In Ramanathapuram district, the abundances of herbs such as Tephrosia purpurea, Crotons sparsiflorus, and Cleome viscosa were significantly lesser in P. juliflora invaded plots as compared to the non-invaded plots. Relative abundance of birds such as Pavo cristatus, Conturnix conturnix and Acridotheres tristis were positively correlated with P. juliflora abundance in Ramanathapuram taluks. The western zone where the habitat dominated by P. juliflora was observed with low abundances of wild ungulates. 6) Driest environment settings of southern zone favored more P. juliflora than other two agro-climatic zones that are comparatively wet. 7) The study found that the impact of Prosopis in the forested landscapes of Tamil Nadu, especially in Sathyamangalam Tiger Reserve seemed to be adversely affecting the distribution of native biodiversity. 8) Dry zone of Tamil Nadu i.e. at Ramanathapuram the groundwater level-soil moisture conditions, humidity and temperature under the canopy cover were better in the habitats dominated by P. juliflora but in the forested landscapes such as in the Sathyamangalam TR, these environmental factors were comparatively lesser than other habitats of the zone. It reveals that P. juliflora in the forested landscape is not good for natural environmental settings as well as the biodiversity of the region. 9) In all zones that were studied in Tamil Nadu, the P. juliflora was observed to be allelopathic that discouraging other plants from growing around them and seems to be toxic to other biotas in ways that allow the invasives to monopolize the space, sunlight, and nutrients at the exclusion of other species. Plant diversity was observed significantly low at P. juliflora dominated habitats than other habitats of Tamil Nadu including in the Ramanathapuram District. In the native habitats of P. juliflora, the other species have developed a mechanism to counter the allelopathy of P. juliflora, but such defense seems to be not available to several native plants of Tamil Nadu. 10) The study could not find any significant impact of Prosopis juliflora and Lantana camara on the productivity of agricultural crops grown adjacent to the dense growth of Prosopis juliflora and Lantana camara on the bund or as a pure stand. 11) Prosopis juliflora, which is adapted to survive and thrive in diverse environments including very harsh dry environments, was a major boon for impoverished people subsisting in the Ramanathapuram District as it provides 3 them with badly needed valuable provisional services; fuelwood, charcoal, animal feed, constructional materials, reclamation of degraded soil, etc, but the Prosopis juliflora was observed to be adversely affecting both environments as well as native biodiversity in other zones of Tamil Nadu. 12) It was found that wetlands in the arid region are highly susceptible to Prosopis invasion and these wetlands were once used by migratory birds in large numbers but not nowadays that is might be due to high abundances of invasive species. 13) Although, alien invasive species such as P. juliflora and L. camara are adversely affecting the native biodiversity especially in the Western Zone and Cauvery Delta but it has livelihood values in the Southern Zone especially Ramanathpuram and adjoining districts of Tamil Nadu. 14) The study also found that the available nitrogen, phosphorus and organic carbon in the soil were high in highly invaded areas compared to less or non-invaded sites especially in the Southern Zone. 15) Economic analyses also revealed that the benefits of the P. juliflora invasion in the southern zone are higher than the costs. However, some aspects such as increased risk of water table and long-term ecological changes were not examined, thus making the total economic valuation incomplete. 16) P. juliflora and L. camara spread can be halted by actions such as clear cutting/up-rooting followed by burning of the stump of P. juliflora and keeping up-side down of stump of L. camara. Alternatively, ways can be found to utilize the existing stands of P. juliflora so that frequent harvesting can exert a check on its expansion in the non-forested landscape. Minimum, 10 years of weed management plan should be made mandatory of all Management Plans of all Protected Areas and other reserve forests of Tamil Nadu to successfully halt the expansion of these invasive species so that the native biodiversity are conserved. 12) The study concludes that complete eradication of P. juliflora and L. camara is inevitable in the forested landscapes and Protected Areas of Tamil Nadu. However, the study recommend that sustainable management and control of P. juliflora may be a better solution than eradication in the Southern Zone.