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Ecology

Lepidochelys olivacea is the world's smallest sea turtle and lays its eggs at Playa Palmeras on Gorgona Island. - Photos: courtesy Grupo Cimad

Erosion Alert at Colombian Beaches

May. 10 de 2012

By: Giovanni Clavijo Figueroa, Unimedios

Over the last year, Bocagrande, in Cartagena, has lost 50 meters of its coastline due to problems stemming from erosion and rising tides (mares de leva). Palmeras, in the Gorgona National Natural Park, is going through a similar situation. The infrastructure, tourism and a unique species of turtle found only there are seriously threatened. Experts point to the need to take action in the affected zones and to recover the coasts.

While the country tries to recover from one of its most extreme series of floods in recent years due to the winter rainy season, some of the coastal zones of Colombia are threatened by climate variability in this region of the continent, according to a study carried out by the research group on Oceanography and Coastal Engineering (Oceánicos) at the Universidad Nacional de Colombia, the Research Center for Environmental Management and Development (Centro de Investigación para el Manejo Ambiental y el Desarrollo – Cimad) and the Universidad de Cantabria (Spain).

The experts point to the need to take action in areas affected by erosion in Bocagrande, Cartagena, to protect the tourism industry, and to recover Playa Palmeras on the island of Gorgona, to conserve a unique species of turtle found nowhere else in the world, the Golfina (Lepidochelys olivacea).

The objective of the Oceánicos group is to analyze the natural dynamics of the Colombian coastal zones (which have not been widely researched until now), generate knowledge and provide solutions for their problems. And at the same time, to call the national government's attention to the need to organize the beaches into natural ecosystems that are constantly affected by changes.

Monitoring the beach

Bocagrande has a vital tourism sector, but it has been affected by climate processes such as rising tides (mares de leva) –which are increasingly intense–, tail ends of hurricanes and coastal erosion, among other phenomena. Over the last 20 years they have changed the natural dynamic of the sea and waves, making them very unstable.

To understand the problem in this context, it is important to note that this is a matter of coastal erosion: the beaches have a certain width (area) for bathers next to the sea, which starts to erode due to big waves and to cover up part of the sandy sediment. The continuity of this process generates a loss of beach area so that the waves end up striking the cliffs, buildings and roads. In Cartagena this process is endangering the sustainability of its infrastructure and the well–being of its population.

At the same time, the rising tides (mar de leva) are a phenomenon that affects the Colombian Caribbean and comprises all of the extreme events that generate flooding on the coast. For example, the sea level may rise due to winds and pressure fronts (meteorological tides). In addition, the waves that reach the beaches can be intensified by cold fronts and/or hurricanes, which make the level of flooding on the coast higher than normal and overwhelm the embankments of the roads, seafronts and buildings.

In Bocagrande there are hotels and homes near the beach that are in danger of being flooded, according to professor and researcher Andrés Osorio, from the Oceánicos group at the Mining Faculty of the Universidad Nacional in Medellín. “To counteract the risk, the government must implement a plan to organize the coasts along with a permanent monitoring program, as well as coastal infrastructure in certain cases, and in others strategies for relocating the population that lives in the most vulnerable zones”.

To measure the erosion, the Universidad Nacional has developed a system that is unique in Latin America to monitor the beaches in real-time. “Using digital cameras, we constantly take photographs which we send over the Internet to an operational center where the erosion of the beaches is analyzed and identified along with the way in which sediments accumulate in certain stretches. This also enables us to measure the currents and quantify the magnitude of the waves”, says the UN researcher.

50 meters less of beach

The monitoring carried out by the researchers a year and a half ago at Bocagrande made it possible for them to see how the beach has lost 50 meters, due to the extreme climatological fluctuations and severe tidal events that occurred during the hurricane season between January and December of 2010.

Osorio warns that “the rising sea level and climate variability associated with the El Niño and La Niña phenomena are a reality that the country has just gone through, and what occurred on the rivers, although it has been more critical, is also happening on the coasts, which are at great risk and threatened; it is just that we have not perceived this”.

Osorio says that tourism, which is one of the main locomotives for Cartagena’s economy, could be significantly reduced because of these threats. “If the beach is eroded, travelers will not have a place to soak up the sun. In response to such destruction, they will surely avoid returning”.

However, their study proposes short, medium and long-term solutions, beginning with an understanding of the coastal dynamic. “If we monitor the beaches, we will have average data and reliable information to enable us to estimate the time of year in which, for example, a hurricane could come through along with its possible impact on the coasts. This would make it possible to take preventive measures”, concludes Andrés Osorio.

The project, financed by the Spanish International Development Agency (Agencia Española de Cooperación Internacional para el Desarrollo - Aecid), has made it possible to address this research problem using state–of–the–art technology.

The Golfina is losing its nest

Playa Palmeras, in the Gorgona National Natural Park, has an area that is approximately 1200 meters long and some 20 meters wide on average at low tide conditions. It is therefore a really short and small beach where the sea turtles of the Lepidochelys olivacea species, commonly known as the Golfina, come from the Gulf of Mexico to lay their eggs.

For more than 40 years, the island was a maximum-security prison, and numerous coconut palm trees were planted on its beach, thus giving rise to its name. These plants grew without any control, occupying ever more space along the sandy edge and colonizing the places available for the turtles to build their nests. Currently, the space available for them to naturally lay their eggs is minimal.

The impact on their nests has been huge because it means they are exposed to the sea, and when the water level rises above what is normal, the nests get washed by the waves, as observed by Diego Amorocho, PhD and executive director of the Cimad. “Between August and December of 2010 we recorded around 28 nests, and in the year–to–date between 80% and 90% have been lost”.

The situation is increasingly critical for this species, which is in danger of extinction, even though Palmeras is one of the few beaches that does not have direct anthropogenic impacts, in other words, there is no pressure on the turtles and their eggs from a human population.

During the 2010 reproductive season, the researchers relocated the nests on a kind of platform to facilitate better incubation, attempting to isolate them from the impact of the tides and the action of the waves. This, however, proved insufficient. “The successful hatching rate was only 34%, compared to previous years when it ranged between 78% and 86%. In other words, 86 baby turtles would emerge from the nest”, according to the director of the Cimad, who has closely followed the behavior of these animals.

Nesting process

Of the seven species of sea turtles that exist in the world, the Golfina is the smallest, measuring between 60 and 70 centimeters and weighing around 45 kilos. They arrive on the Pacific coast of Colombia between July and November to lay their eggs in a 60 cm deep nest that the female digs. There she deposits an average of 100 eggs, which take between 45 and 50 days to complete their incubation period. When the young emerge, they go to the edge of the beach and then begin to walk to the sea; 30 or 40 years later, if they are lucky enough to survive to adulthood, the females return to lay their eggs on the same beach where they were born.

For Amorocho, “this place has a very dynamic oceanographic and climatological process, and what is happening can affect the sandy border available for the turtles to nest. The worst thing is that the growth and colonization by the coconut palms towards the sea is taking away this species’ space for egg laying”.

That is the finding of the Oceánicos group from the UN that he leads, which last year began a project to evaluate the impact on the Golfina of the palms and beach erosion and accretion processes. This knowledge will enable them to propose alternatives for conservation of this species.

With the approval of the National Parks Unit, an attempt will be made to selectively modify the area where the vegetable species are planted. The idea is to enlarge the space available for the turtles’ normal reproduction towards the land in order to protect the existence of this species on the Colombian Pacific coast, which has a crucial role in the ecosystem.

“The sea turtles are indispensable for maintaining the balance of the marine ecosystems and play an important role as elements for the flow of nutrients between the land and maritime environments. The baby turtles have an ecological function on land because they serve as food for other species that prey upon them, such as crabs, marine birds and small mammals. In this way, the stability of the trophic chain in the beach ecosystem is maintained”, asserts Diego Amorocho.

In addition to the Oceánicos group from the UN and the Fundación Cimad, the National Parks Unit also takes part in the Playa Palmeras research project, with support from the Fund for Environmental Action and Children (Fondo para la Acción Ambiental y la Niñez) as well Conservación Internacional.



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