The Ciénaga Grande de Santa Marta, located in the Department of Magdalena, forms the Estuarine Delta System of the Magdalena River and extends to the Caribbean Sea. Its ecosystem assets include the largest mangroves in the Colombian Caribbean, continental wet areas, coastal lagoons, forests, agricultural and transformed land types. The site supports fisheries and agriculture and provides carbon storage, habitat and other services to local communities. It also carries a series of overlapping conservation designations, including a flora and fauna sanctuary, a biosphere reserve, an important bird area, the Salamanca Island Park and Ramsar status. The Ramsar designation dates to 1998.

The wetland’s condition depends on the interaction between freshwater and seawater throughout the year. This exchange shapes water salinity, while changes in river flow alter the salinity of mangrove soils and influence both vegetation and fisheries. Diversion of water from rivers descending from the Sierra Nevada de Santa Marta for agriculture, together with construction of the Barranquilla–Ciénaga and Palermo–Sitio Nuevo roads, has altered exchange inlets and reduced connectivity between the Magdalena River and the lagoon complex. An integral environmental recovery program initiated by INVEMAR in the 1990s included dredging a five-channel network to restore water exchanges among the Magdalena River, lagoon bodies and the Caribbean Sea. Monitoring of the resulting hydrological regime continues, with hydro-sedimentological observation beginning in 2017.

These pressures complicate an ecosystem already affected by climatic variability. Strong and very strong El Niño events in 2015 and 2016 were associated in the study with reduced rainfall in the Colombian Caribbean, increased mangrove-soil salinity and hydrological stress. In 2017, a Ramsar advisory mission found strong changes in the wetland’s ecological characteristics associated with water-balance loss and human intervention, leading to its inclusion in the Montreux Record. The new study combined environmental and socioeconomic data into a spatial account intended to show how changes in ecosystem extent and condition affect the supply of services and the associated economic value.

For the extent account, researchers compared two CORINE Land Cover layers mapped at a scale of 1:100,000, representing 2012 and 2018. They standardized the land-cover classifications, calculated geodesic areas and used spatial intersections to construct a transition matrix showing opening extent, gains, losses and closing extent. Pastures, continental wet areas and mangrove forests recorded the largest losses during 2012–2018, while permanent crops, heterogeneous agricultural areas and areas with herbaceous or shrub vegetation recorded the largest gains. Mangroves, continental wet areas and pastures mainly transitioned into agricultural or transformed-cover classes. The analysis identified where losses occurred but could not attribute each gain or loss to a specific natural event or human action.

Condition accounts were possible only for mangroves and coastal lagoons and covered 2017–2019 because of data availability. The framework classified condition variables under abiotic, biotic and landscape characteristics. Mangrove indicators included basal area, seedling and propagule density, interstitial salinity, bird species richness and change in extent related to water. Coastal-lagoon indicators included dissolved oxygen, total suspended solids, surface salinity and fish species richness. Reference levels drawn from monitoring reports, regulatory criteria, bibliographic sources and observed salinity ranges were used to rescale variables and construct aggregate condition indices.

The two monitored ecosystem types showed different trends. Mangrove condition had a net positive change from 2017 to 2019 because abiotic values rose as interstitial salinity declined, biotic values rose with greater bird richness and more seedlings and propagules, and landscape values improved as mangrove area expanded. Basal area decreased during the period, showing that recovery was not uniform across every measured characteristic. Coastal lagoons recorded a net negative change: dissolved oxygen declined, surface salinity increased and fish species richness fell. The contrasting aggregates demonstrate how condition accounting can distinguish environmental improvement in mangrove forests from deterioration in adjacent lagoon waters.

Mangrove extent increased by 3,503 hectares during 2017–2019, equivalent to a reported recovery of 6.87% relative to the 51,150 hectares recorded in 1956. The researchers associated this increase with freshwater inflows through dredged channels connected to the Magdalena River and with the absence of El Niño-related events during part of the accounting period. Bird richness also increased, with 98 species recorded in 2019. The list included the northern screamer, sapphire-bellied hummingbird and bronzed cowbird, together with numerous migratory species. These observations describe improvement within the selected indicators and period; they do not establish that every component of the lagoon complex recovered.

Fishing-resource data showed how environmental variation appeared in a service used by communities. SIPEIN records showed total artisanal catch ranging from 4,617 to 6,035 tonnes per year between 2015 and 2019, a net difference of 721 tonnes per year between the opening and closing years. Fish contributed the largest catches, followed by crustaceans. Mollusc catches were not collected in 2018–2019 because of logistical problems, so the reported total underestimates those resources in those years. Catch fell sharply in 2016, coinciding with the highest salinity records in two decades, and subsequently recovered as salinity declined and the composition of the fishery shifted among estuarine, marine and freshwater species. The account therefore documents an association between salinity, climate variability and recorded catches rather than isolating the contribution of any one factor.

The climate-regulation account focused on mangrove carbon. Aboveground carbon was estimated from tree diameter and biomass relationships, while belowground estimates were drawn from measurements covering the upper metre of soil. Carbon stocks were valued using Colombia’s carbon tax rate, set at USD 5 per tonne of carbon dioxide in 2017 with annual adjustment. Aboveground carbon content declined across the principal mangrove types over 2015–2019, leaving total mangrove carbon 16.5% lower in 2019 than in 2015. Most of the decline occurred between 2015 and 2017, when mangrove loss, hydrological stress, desiccation and charcoal burning were associated with carbon emissions rather than sequestration. Physical carbon stocks rose during 2018 and 2019, but their monetary value declined as the Colombian peso depreciated against the dollar. Soil-carbon estimates are incomplete because the reference measurements covered only one metre, while mangrove carbon reservoirs extend deeper.

The monetary asset account placed the value of mangrove carbon stocks at USD 68.3 million in 2015 and USD 55.13 million in 2019. Annual wild-fish supplies from mangroves and coastal lagoons were converted to asset values using a net-present-value method with a 100-year asset life and a 3.5% social discount rate. The combined mangrove and coastal-lagoon asset estimate was USD 105.71 million in 2015 and USD 97.27 million in 2019. The resulting difference of USD 21.61 million comprised USD 13.17 million in mangrove losses and USD 8.44 million in losses for the combined coastal-lagoon and mangrove category. These are accounting estimates, not observed losses of cash or conventional market assets. They provide a way to place ecosystem assets and service flows on the same statistical framework as economic activity.

The pilot also exposes important constraints. Catch is recorded at four landing places and distributed across the wetland, rather than assigned to the specific mangroves, lagoons or marine areas that produce it. This prevents precise attribution of fishing benefits within an interconnected coastal landscape. The condition accounts do not include all six classes in the SEEA EA condition typology, and the land-cover transition analysis cannot determine whether individual changes resulted from El Niño, farming, infrastructure or another pressure. Fishers’ income also cannot be inferred from physical catch alone because market prices, price elasticity, consumer preferences and pre-sales arrangements affect the revenue received. Even with those limitations, the account establishes a baseline for monitoring the extent, condition and service flows of a Ramsar wetland and offers Colombia a spatial framework for integrating ecosystem information into environmental statistics, biodiversity reporting and economic planning.

Subject of Research: Pilot ecosystem accounting of Colombia’s Ciénaga Grande de Santa Marta Ramsar Site

Article Title: Accounting of marine and coastal ecosystems at the Ramsar Site, Estuarine Delta System of the Magdalena River, Ciénaga Grande de Santa Marta, Colombia

Article References: Gomez Cardona, C., Moreno, J., Contreras, A., Sanchez-Nuñez, D., Arciniegas Moreno, N., Guerrero, D., Viloria Maestre, E., & Lopez Navarro, J. (2023). Accounting of marine and coastal ecosystems at the Ramsar Site, Estuarine Delta System of the Magdalena River, Ciénaga Grande de Santa Marta, Colombia. One Ecosystem, 8, Article e98852. https://doi.org/10.3897/oneeco.8.e98852

Image Credits: AI Generated

DOI: 10.3897/oneeco.8.e98852

Keywords: Ciénaga Grande de Santa Marta, ecosystem accounting, SEEA EA, mangrove carbon, coastal lagoons, artisanal fisheries, wetland condition, natural capital, El Niño, Ramsar Site, Accounting, marine