Table of Contents
Anthropogenic Pressures on Wetlands: Thol Bird Sanctuary Case Study
Last Updated: August 31, 2025
Introduction
Have you ever wondered which human activities most quietly reshape a wetland? Anthropogenic Pressures on Wetlands — from oil wells to cattle grazing and tourism — can change water, sediment and biodiversity faster than you think. At Thol Bird Sanctuary, the Ph.D. thesis by M. H. Bhadrecha (2018) documents these pressures and their ecological consequences. This post pulls verbatim thesis excerpts (with exact page numbers), explains complex effects in plain language, and gives clear, actionable management recommendations. Read on to learn which pressures matter most and how to prioritize responses.
Overview of observed pressures
“Thol Wildlife Sanctuary, having a wetland with a potential of internationally importance and among the eight national wetland sites has been identified and declared for conservation. This wetland is also found to be facing human disturbances like Oil drilling by ONGC, live stock grazing, wood extraction, agriculture in nearby areas and withdrawal of water for irrigation (Plates 1.1 A to J).” (p. 4)
Thol is important, but it faces multiple human pressures at the same time — not a single threat. These combined stresses interact and can amplify damage.
Tourism, litter, and recreational impacts
“Tourists visits: Tourists visits from nearby villages as well as from distant places like Ahmedabad. The number of tourist visit and revenue generation at Thol Wetland is as per Table no. 1.1. Tourists were seen roaming on ‘bundhs’ and on inner periphery of West–South side of the wetland and also playing games at some spots. According to a survey, 84% tourists came for picnic/recreation, 14% came for bird watching and only 2% came for photography/filming (Sasikumar K., 2014). This pattern undermines the real significance of Thol Wildlife Sanctuary among the tourists, especially as an important Bird destination site.” (p. 4)
Most visitors treat the sanctuary like a picnic ground. That means trampling, litter, and disturbance of birds — while the site’s core conservation role is sidelined.
Oil wells and contamination risk
“ONGC oil wells: ONGC wells are not only scattered throughout the catchment area but also located in the Sanctuary itself especially towards the southeast and northern areas of the Sanctuary. There are total 21 numbers of oil wells out of which 13 are functional, polymer injection wells are 3 in number and chase water wells are 5 in numbers. The total oil production from Thol ONGC wells is about 105 tpd. Although no major oil spill or its consequent effects have been reported at Thol sanctuary, ditches filled with oil and soil stained with oil were observed during the study at more than one wells (Plates 1.1 F).” (p. 4)
Active oil operations inside and near the wetland are a major, ongoing risk. Even without a major spill, local oil-contaminated soils and ditches can leach contaminants into water and sediments.
Grazing, washing, and small-scale pollution
“Cattle wading and Cattle grazing: The livestock like buffalo, sheep and goats were finding their way from the open side (catchment area) into the sanctuary area and were grazing on the dry region especially on the mid to Northern area of the TWS wetland. Cattle wading were observed mainly in the stagnant water (almost 3 feet deep) towards South – East corner of TWS wetland.” (p. 4)
“Cloth Washing: Cloth washing activity (very small scale) was going on towards the North West side and South – East side of TWS wetland on few of the occasions.” (p. 4)
Plain English: Everyday human uses — grazing and washing — directly alter shoreline and shallow-water habitats. These activities increase suspended solids, nutrients, and direct biological disturbance.
Agricultural runoff and eutrophication risk
“There is a possibility of the pesticides and fertilisers used in the catchment area to find their way into the Thol wetland in the form of agriculture runoff. Leaching of fertilisers containing nitrogen and phosphorus contribute to the nitrates and phosphates could cause eutrophication in the wetland.” (p. 5)
Plain English: Runoff from nearby farms carries nutrients and agrochemicals into the wetland, increasing the risk of algal blooms, oxygen depletion, and food-web disruption.
Plastic and municipal waste
“Plastic trash: The area is declared Plastic Free Zone by the Forest Department. Even though, some tourists were found littering on few spots by leaving their rubbish Plastic trashes like wrappers, fast food packages, bottles etc. However it was also noted that these plastic trashes were also being picked up by the daily wagers deployed by the Forest Department (Plate 1.1 A to J).” (p. 5)
Plain English: Despite rules, plastic litter remains, posing entanglement and ingestion risks to wildlife and degrading aesthetic and ecological value.
Compound effects and monitoring gap
“Keeping all above in mind, the study began with the preliminary survey of Thol wetland and a review on that, we found out there is a still a space and necessity for an organised study of various components for Thol Wetland. Especially, there is a deficiency on the study of ‘Organic Load’ reflecting parameters like BOD, COD, TOC, nutrient parameters & trace metals with a substantial sampling frequency and study duration.” (p. 10)
Plain English: The researcher found an evidence gap — organic load, nutrients and trace metal monitoring were insufficient. Without systematic, frequent data, managers risk missing slow-building problems.
Spatio-temporal patterns of pressure and ecological response
Seasonal water dynamics shape how human pressures play out. During monsoon, pulses of runoff can deposit sediments and contaminants but also dilute dissolved pollutants. In summer, water shrinks, concentrating pollutants and exposing shoreline areas to grazing and trampling.
Location differences are crucial. The thesis sampled three locations with different human-use profiles: a catchment inflow/core zone, a tourism/transition zone, and a deeper permanent pool (pp. 39–40). Each location showed different vulnerability:
- Catchment/core: benefits from inflow dilution but faces upstream agricultural inputs.
- Tourism/transition: highest direct disturbance (trampling, litter, washing).
- Deep pool: retains water year-round and can act as contaminant sink, risking bioaccumulation.
Interaction effects: For example, near ONGC wells, oil-stained soils plus seasonal runoff can transfer hydrocarbons into sediments, where benthic macroinvertebrates can accumulate toxicants, altering the food base for birds (see Chapters 5 & 5.3).
Ecological consequences explained simply
Water quality shifts. Increased nutrients cause algal blooms; subsequent decomposition lowers oxygen (BOD rise), stressing fish and invertebrates.
Sediment changes. Erosion and runoff increase suspended solids and deposit fine, organic-rich sediments that bind trace metals.
Benthic community changes. Sensitive taxa decline; tolerant taxa (certain worms, chironomids) dominate — reducing food quality for birds and fish.
Bird impacts. Foraging habitats (shallow shoreline zones) are altered by trampling, sedimentation, and reduced benthic prey, affecting migratory and resident waterfowl counts.
Priority management actions
- Map and prioritize pressures — use the thesis’ location map to identify hotspots (tourism nodes, ONGC well clusters, inflows).
- Strictly regulate oil operations inside sanctuary — immediate containment, regular inspections, and remediation plans for oil-stained pits.
- Control shoreline access — provide designated viewing platforms and marked trails to reduce trampling and disturbance.
- Manage tourism behavior — shift visitor use from picnicking to guided birdwatching; enforce no-plastic rules with fines and education.
- Grazing and washing controls — create buffer zones and community-managed washing sites away from sensitive shoreline.
- Agricultural runoff mitigation — promote vegetated buffer strips and farmer outreach on fertilizer use.
- Routine integrated monitoring — seasonal sampling for physico-chemical, sediment, benthic macroinvertebrates and primary productivity.
- Community engagement — train local stewards for litter patrol, simple biomonitoring, and visitor guidance.
- Emergency response plan — develop oil-spill and contamination response procedures coordinated with ONGC and forest authorities.
Quick implementation roadmap (short bullets)
- 0–3 months: hotspot mapping, trail marking, small-scale visitor education.
- 3–9 months: implement buffer vegetation, grazing controls, begin seasonal monitoring.
- 9–18 months: oil well risk audits, remediation planning, community stewardship programs.
- 18+ months: evaluate trends, adapt management based on monitoring data.
Conclusion
Anthropogenic Pressures on Wetlands at Thol are multiple and interacting: oil operations, tourism, grazing and runoff together drive water, sediment and biodiversity change. Prioritizing containment of oil risks, tourism regulation, runoff control, and integrated monitoring will yield the best conservation outcomes.
FAQs
Q: Which pressure is most urgent at Thol?
Active oil operations inside the sanctuary are the highest-risk due to their potential for persistent contamination.
Q: Can tourism be sustainable at Thol?
Yes — by shifting visitor behavior to guided birdwatching, restricting picnic zones, and enforcing no-litter rules.
Q: How often should monitoring run?
Seasonally at minimum (monsoon, winter, summer); monthly during critical transition periods if possible.
Author Bio
Researcher: Dr. M. H. Bhadrecha — Ph.D., Department of Zoology, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara (2018). Research Guide: Prof. P. C. Mankodi.
Source & Citations
Thesis Title: Ecosystem Assessment of Thol Bird Sanctuary with Special Reference to Benthic Macroinvertebrate Community
Researcher: Dr. M. H. Bhadrecha
Guide (Supervisor): Prof. P. C. Mankodi
University: The Maharaja Sayajirao University of Baroda, Vadodara
Year of Compilation: 2018
Excerpt Page Numbers Used: pp. 3–5, 10–12, 39–41, 54, 62–66, 84–88, 95–103
Disclaimer: Some sentences have been lightly edited for SEO and readability. For the full, original research, please refer to the complete thesis PDF linked in the section above.
Do you agree that oil operations inside a sanctuary should be the immediate management priority? Share your view and tag a wetland manager.
Discover more from Professor Of Zoology
Subscribe to get the latest posts sent to your email.