Sea Level Rise at Junquillal – Modeling Future Coastlines

In this second installment of a three part series on WWF’s Latin American and Caribbean Program's coastal adaptation projects in Costa Rica, Ana Fonseca, the Latin America and Caribbean lead with WWF-LAC, together with Carlos Drews discusses the community’s efforts to adapt – both for the turtles and themselves.

The fortunes of coastal communities like Junquillal are intimately tied to the sea and the shoreline that sits just meters away from houses and roads, a relationship shared by species like sea turtles, for whom the beach is the sole nesting site. Coastlines are not static however, but instead shift according to storms, currents, and changing sea levels. Scientists warn that the sea-level could rise by at least one meter by the end of the century due to climate change, threatening both coastal communities as well as critically important turtle nesting sites like Junquillal.

But what would a one meter rise mean for Junquillal? To answer this question, my team and I at WWF-Latin America and the Caribbean, in collaboration with the Spanish company Stereocarto, developed flooding models for Junquillal under different scenarios of sea level rise. The flooding was simulated for 5.6 km of beach, including 500 m inland, based on a high resolution elevation model from a laser altimeter (LIDAR). Flooding models are needed to more effectively plan coastal development and protected areas, in such a way that both sea turtles and the local population benefit.

In June 2009, a small Piper aircraft, equipped with simultaneous LIDAR and digital photography technology, flew over Playa Grande and Junquillal Beach. The flights took place in the morning, and the resulting photographs portray the conditions and shoreline at low tide. During the flight, laser data were captured with a LIDAR sensor to generate the Digital Terrain Models (DTM) and Digital Surface Models (DSM) from the lowest low tide point to 500 m landward, with a resolution of 4 to 5 points/m2 and with an altitude precise to within 15 cm. Finally, aerial photos were taken as well. The images were combined using a three dimensional vision system called Stereocaptor to produce animations of the possible flooding of Playa Grande and Playa Junquillal under different sea level rise scenarios (from 0 to 150 cm, at 10 cm intervals). 

Watch the following animation to see the projected change in Junquillal's coastline: 

All of this technical analysis made it clear that the town as we know it in 2010 and the critically important turtle nesting beaches may be radically altered by rising sea levels. The models revealed that sea level rise would push the shoreline inland from its present location and that most of the flooding in Junquillal would start from behind the village (that is, from the inland side) as the sea would first flood the area around the mouth of Nandamojo river and its estuary and wetlands (mostly mangrove forest) that lie alongside the village. The destructive force of the rising seas will cause erosion, threatening both the town’s infrastructure and the turtles’ nesting area.

Analytical models such as these are not 100% accurate. Despite the uncertainty, it’s clear that the citizens of Junquillal must take stock of their village’s future, both for themselves and the turtles that nest there. Of course, the Junquillaleños don’t want to lose their houses and the turtles’ nesting areas, but before they can take action, they must first acknowledge that sea level rise is happening and the flooding risks it poses are realistic.

The future of Junquillal depends on its ability to move away from the coast and the rising sea, and still maintain the ecological conditions suitable for the leatherback turtle to nest. It’s crucial that this region’s land use plan include climate change adaptation measures such as infrastructure setbacks, to protect both current and future investments like the beaches and their sea turtles. The implementation of these adaptation measures for nesting beaches is an international commitment of the Inter-American Convention for the Protection and Conservation of Sea Turtles, of which Costa Rica is a signatory. By implementing such measures, both people and turtles will have a better chance to cope with sea level rise and Costa Rica will continue its regional leadership in sea turtle conservation and as a worldwide role model in biodiversity conservation.