by Jainam S Jain
A single Olive Ridley Sea Turtle can lay about 110–140 eggs, and reports indicate that just one out of every thousand hatchlings that enter the sea grows to full adulthood (Kumar et al 33). In recent years, the Orissa Olive Ridley population has experienced severe mortality with over ten thousand turtles being counted dead on the shore each year just due to fishery-related accidental death. Before reaching the vast oceans, the eggs and hatchlings must survive through a lot of problems. As a result of their exceedingly low survival rate, they have been placed on the International Union for Conservation of Nature’s “red list”. This vulnerability is a result of their habitats being destroyed by various significant activities (Kumar and Ghosh). Unless the situations that threaten their survival and reproduction improve, they might be on the verge of extinction. This paper intends to investigate that it is not only fisheries that are to be blamed for the decline of these vulnerable turtles but factors like climate change, predators, and developmental activities too. Year after year, natural and anthropogenic pressures on the turtle fauna at the rookeries are increasing. Threats to nesting environments are described as any action or procedure that has the potential to modify the sand substrate of the nesting beach, damage or kill sea turtles or their eggs or disturb regular behavior patterns. (Witherington 1). There are numerous other potential reasons associated with the downfall of these turtle populations.
The Pacific Ridley Sea Turtle, often known as the Olive Ridley Sea Turtle (Lepidochelys olivacea), has been on this planet even before dinosaurs existed. These species of turtle belong to the Cheloniidae family. These turtles are the most abundant among all the turtles on the planet and one of the smallest of their kind. Olive Ridley turtles can be found almost anywhere in the world’s tropical waters. These turtles have an obvious global significance of mass nesting rookeries in the tropics, especially in Orissa, known for having the highest number of nesting in the world, La Escobilla in Mexico, and Playa Ostional and Playa Nancite in Costa Rica are also major mass-nesting rookeries (Shanker 3). Gahirmatha marine sanctuary, Rushikulya Rookeries, and the river mouth of Devi are the prominent places where Arribadas occur. The rest of the coastline finds sporadic nesting on them.
Due to global warming, the turtles will be among the first victims of climate change, as the gender of the hatchlings depends a lot upon the temperature. Warm incubation temperatures result in female hatchlings whereas cooler incubation temperatures result in male hatchlings. As sand temperatures rise on nesting beaches, the sex ratio of hatchlings becomes virtually exclusively female and this might create an imbalance in their sex ratio. Sumedha Korgaonkar, who is an expert on Olive Ridley turtles, states that these eggs can withstand a temperature of up to 33 degrees Celsius, and an optimum temperature of 29.5 degrees Celsius is required to keep the sex ratios balanced (qtd. in Gayakwad). This will pose a threat to the turtle population as their process of reproduction will decline.
Apart from the change in the possible sex ratio, climate change affects the turtles’ habitats, food sources, and nesting activities adversely, as the oceans are getting warmer with time. Cooler oceans provide more food sources for sea turtles as they are more suitable for fish to reproduce. Also, oxygen levels in warm waters are less than normal which makes it harder for Olive Ridley turtles to breathe underwater.
The sea level rise is taking away the space that these turtles use for nesting and breeding on beaches, thus resulting in fewer hatchlings. Several observations were made by the scientists present in the Arribadas as the female ridleys started scooping out sand with her flippers for making a pot-shaped chamber to create space for nesting, inadvertently scooping out eggs laid by another female earlier (Mundappa). A female crawled over another female who was busy laying her eggs further ahead. She chose a nest less than a meter away from the first female, and when she began digging, she completely covered her neighbor in the sand (Mundappa).
The abrupt and dramatic changes in coastal morphology are caused by episodic coastal hazards linked with cyclonic storms (Grases 346). Because of the longer monsoon season, the peak hatching period, which usually concludes by the end of March, has been extended until April-May. The eggs are destroyed by beach erosion induced by southwest winds immediately before they can hatch. Net loss due to inundation and erosion accounted for 23% of overall nesting loss due to natural factors at the Gahirmatha rookery (Behara 438). The Olive Ridleys usually prefer clean and warm beaches to nest but after the cyclones, the beaches are full of debris which makes the location less favorable for them.
On October 29, 1999, Orissa was pummelling by a Super Cyclonic Storm that made landfall near Paradip. The estimated maximum wind speed in the core area was 260-270 kmph, resulting in a massive storm surge that caused a sea-level elevation of more than 20 feet and the loss of approximately 10,000 lives. It was accompanied by unusually severe rainfall, which caused deadly floods and blocked the state off from the rest of the country (Kalsi 1). This Super Cyclone wreaked havoc on the shoreline, eroding beaches and destroying numerous key nesting sites that had been fragmented into islands or were submerged beneath the waves. As a result, many eggs were inundated in the oceans, which did not provide suitable conditions for hatching. Since 1999, mass turtle nestings have happened on alternating years, occasionally after a 2–3-year interval as well.
The Rushikulya rookery on India’s east coast is one of the major mass breeding areas for Olive Ridley sea turtles. This yearly mass nesting event (arribada) is triggered by finely interwound geo-ecological cues, which are frequently interrupted by anthropogenic influences and extreme weather phenomena like tropical cyclones. The impact of category five storm Fani (which made landfall on 03 May 2019, summer rather than autumn) on the Rushikulya rookery was studied for the first time using remote sensing and GIS technology (Mishra), as very severe but untimely cyclones are expected to become more common as a result of climate change. The beach along the Rushikulya rookery withdrew a hundred meters inward as a result of storm Fani (2019), which led to a halt to mass nesting that year (Mishra). The fragmentation of the spit, which appears to be a necessary habitat and protective structure for successful mass nesting, was the most noticeable aspect. Due to the spit’s natural reconstruction and potentially cyclone-driven nutrient enrichment, the next year (2020) saw an extremely successful mass nesting. This study will serve as the first baseline data on the anticipated impact of such extreme weather events on migratory marine turtles in India.
Amlan Nayak, the divisional forest officer (DFO) in Berhampur estimated that 15% – 20% of the record 5.5 lakh eggs deposited by sea turtles in the five-kilometer-long nesting sites from March 28 to April 4 (2022) may have been harmed due to cyclone Asani and beach erosion. Since March 25, around 5.01 lakh sea turtles have come to the Gahirmatha Marine Sanctuary in Kendrapara district for mass nesting (arribada) for over 4 days, he said (India). As the turtle nestings were high this year, there were high expectations of good hatches but due to the cyclone, high tides, and soil erosion, the numbers went lower.
Furthermore, Biswas Pandav in the Indian Ocean Turtle Newsletter has said that Casuarina plantations in Orissa are believed to have had negative impacts on nesting beaches and the process of nesting itself (27). The plantation has disrupted Orissa’s coastal ecology and resulted in environmental degradation of the shore. To mitigate the effects of cyclones in the region, Casuarina was imported from Australia and widely planted on the beaches, which acted as a cyclone barrier and shelter belt, thus preventing beach erosion (Pandav 27, Schmid 215). But the plantations changed the topography of the beach through their root growth. This has the potential to significantly impede natural processes along the coastal system.
Casuarina is recognized to be detrimental to nesting Olive Ridley populations in multiple ways. Devi River mouth has lost much of its nesting habitat due to the plantations. While 50% of Rushikulya’s mass nesting beach is devoid of the plantation, the remaining sections are surrounded by extensive Casuarina plantations (Tripathy 439). The eggs and hatchlings get entangled in the thick root masses and litter fall which destroys them. Natural predators like jackals, hyenas, monitor lizards, wild pigs, crabs, etc. breed in dense vegetation near coastal dunes, putting additional predation pressure on nesting females, eggs, and hatchlings. Jackals and dogs prey on the nests that are built inside the Casuarina plants.
Furthermore, under natural conditions, after they emerge from the nest, the Olive Ridley hatchlings move directly toward the sea. The offsprings need light to follow, so the moonlight on the waves guides them toward the ocean (Pandav 26). On their way to the ocean, most of them die of dehydration and exhaustion or get eaten by predators. Any form of artificial light source present near the nesting beach can interrupt the hatchlings’ sea-finding behavior because they tend to go towards the source of light instead of the sea. The lights installed in coastal regions as a product of development are much brighter than the moonlight, which misdirects them away from the sea. This way the baby turtles either get crushed by the humans or fed on by stray dogs or crows. This effect on the hatchlings is known as Hatchling Disorientation and it happens at Rushikulya rookery to a large extent.
Furthering the coastal development and making the situation worse for the turtles is the construction of new water sports and coastal highways near the nesting habitats (Behara and Tripathy). The seaports are made to connect with landlocked states like Chhattisgarh, Jharkhand, Bihar, and Uttar Pradesh. This is further reducing the area for the turtles to breed and nest. The extensive dredging of shipping channels may influence water turbidity and light penetration, as well as benthic habitat, with possible consequences for the entire food chain, including the Olive Ridley turtles. This development will lead to more infrastructure and tourism on the coastline, further increasing marine and light pollution and making it difficult for the turtles to survive. There are chances of oil spills happening in this region due to the establishment of ports, cargo ships, and many petroleum-based industries.
Turtles graze on some organisms to keep the ecology balanced and they are also a vital source of food for other creatures, especially when they are young and easy to predate. Vultures, frigate birds, crabs, raccoons, coyotes, iguanas, and snakes prey on hatchlings as they make their way across the dunes to the ocean (Tripathy 442). Possible hatchling predators in the water include oceanic fishes, sharks, and crocodiles. Except for sharks, adults have few known predators, although killer whales are occasionally responsible for assaults. Jaguars may pose a hazard to females that are breeding on land. Notably, the jaguar is the only cat with a powerful enough bite to pierce a sea turtle’s shell. This inevitably leads to a significant decline in the number of turtle nests, eggs laid, hatchlings, and turtles.
To conclude the research, the population of the Olive Ridleys has drastically fallen in the last three decades due to changes in the climate causing more frequent cyclones. To mitigate the aftermath of these cyclones, casuarina plantations were brought in. Unfortunately, this backfired on the turtles, resulting in a further decline in their population. In addition to these, developmental activities such as the building of ports and defense facilities, laying of coastal roads, and development to support the increasing tourism, have significantly impacted the population of these turtles. Furthermore, predators have a key role in the decline of these populations as the turtles are the main source of their diet. All these factors have together vastly influenced the population of Olive Ridleys in the seas.
WORKS CITED
Barik, Shraban K., et al. “Environmental Cues for Mass Nesting of Sea Turtles.” Ocean & Coastal Management, vol. 95, 2014, pp. 233–240., https://doi.org/10.1016/j.ocecoaman.2014.04.018.
Behera, Satyaranjan & Tripathy, Basudev & Kuppusamy, Sivakumar & Choudhury, Binod & KAR, Chandrasekhar. “Nesting Habitat Suitability for Olive Ridley Turtles (Lepidochelys Olivacea) at the Gahirmatha Rookery, Odisha Coast of India”, International Journal of Conservation Science.2013, 4, 477-484
Behera, Satyaranjan & Tripathy, Basudev. “Review of Current Developmental Activities And Their Possible Impact on Olive Ridley Sea Turtles Along the Odisha Coast of India, 2017, Testudo Vol. 8, No. 1, pp no. 38-55
Behera, Satyaranjan, and Hinrich Kaiser. “Threats to the nests of Olive Ridley Turtles in the world’s largest sea turtle rookery at Gahirmatha, India: need for a solution”, Herpetology Notes, 2020, vol. 13, pp no. 435-442
Grases, Albert, et al. “Coastal Flooding and Erosion under a Changing Climate: Implications at a Low-Lying Coast (Ebro Delta).” Water, vol. 12, no. 2, 2020, p. 346, https://doi.org/10.3390/w12020346.
Press Trust of India. “Thousands of Olive Ridley Turtles Eggs Washed Away Due to Asani’s Impact.” NDTV.com, NDTV, 12 May 2022, https://www.ndtv.com/india-news/odisha-cyclone-asani-turtle-eggs-thousands-of-olive-ridley-turtles-eggs-washed-away-due-to-asanis-impact-2969566.
Kalsi, S. R. “Orissa Super Cyclone – A Synopsis.” MAUSAM, vol. 57, no. 1, 2006, pp. 1–20., https://doi.org/10.54302/mausam.v57i1.449.
Kumar, Manish, and Sahana Ghosh. “Olive Ridleys Day-Nest in Odisha after Seven Years, but No Link to Lockdown Say Experts.” Mongabay, 1 Apr. 2020, https://india.mongabay.com/2020/04/olive-ridleys-day-nest-in-odisha-after-seven-years-but-no-link-to-lockdown-say-experts/.
Kumar, Suresh & John, Sajan & Kuppusamy, Sivakumar & Choudhury, Binod. “Egg-laying duration in the olive Ridley turtle Lepidochelys olivacea and its relevance for the estimation of mass nesting population size”, The Herpetological Journal, 2013, 23. 23-28.
Mishra, Manoranjan, et al. “Vulnerability of Nesting Ground of Olive Ridley Turtle to Severe Cyclonic Storm Fani: A Case Study from Rushikulya Rookery, East Coast of India.” Journal of Coastal Conservation, vol. 25, no. 4, 2021, https://doi.org/10.1007/s11852-021-00827-2.
Mundappa, B. “When a Million Turtles Land.” Maptia, 2015, https://maptia.com/kalyanvarma/stories/when-a-million-turtles-land.
Pandav, Biswas. “Casuarina Plantations along Sea Turtle Nesting Beaches in Orissa.” Letters to the Editor, 2005, pp. 26–28., https://doi.org/https://www.iotn.org/wp-content/uploads/2015/10/01-11-LETTERS-TO-THE-EDITOR.pdf.
Rahul Gayakwad / TNN / Updated: Apr 7, 2022. “Climate Changes Make Olive Ridleys Arrive Late, Stay Longer: Kolhapur News – Times of India.” The Times of India, TOI, 7 Apr. 2022, https://timesofindia.indiatimes.com/city/kolhapur/climate-changes-make-olive-ridleys-arrive-late-stay-longer/articleshow/90695402.cms.
Tripathy, Basudev & Rajasekhar, P. “Natural and anthropogenic threats to olive ridley sea turtles (Lepidochelys olivacea) at the Rushikulya rookery of Orissa coast, India”. Indian Journal of Geo-Marine Science, 2009, 38, 439-443.
Schmid, Jill L., et al. “The Effect of Australian Pine (Casuarina Equisetifolia) Removal on Loggerhead Sea Turtle (Caretta Caretta) Incubation Temperatures on Keewaydin Island, Florida.” Journal of Coastal Research, vol. 10055, 2008, pp. 214–220., https://doi.org/10.2112/si55-001.1.s
Shanker, Kartik. “Marine Turtles in the Indian Subcontinent: A Brief History.” Marine Turtles of the Indian Ocean, edited by B C Choudhury, Orient Longman Private Limited, Chennai, Tamil Nadu, 2006, pp. 3–16.
India Ocean Project 