UNAM Study Reveals Dramatic Loss of Mexican Mangroves in 5 Years

A significant decrease in the extent of mangroves in Mexico's northwest region has been reported. The area has lost an estimated 1,817 hectares from 2015 to 2020, according to a study conducted by the Institute of Marine Sciences and Limnology (ICMyL) of the UNAM and the National Commission for the Knowledge and Use of Biodiversity (Conabio). The researchers used the Google Earth Engine platform to analyze the data.

The study was a collaborative effort between ICMyL researchers Francisco Flores de Santiago and Francisco Javier Flores Verdugo, and Conabio's Luis Valderrama Landeros, Carlos Troche Souza, José A. Alcántara Maya, Samuel Velázquez Salazar, Berenice Vázquez Balderas, Edgar Villeda Chávez, María I. Cruz López, and Rainer Ressl. The research focused on the northwest coast, including Baja California, Baja California Sur, Sonora, Sinaloa, and Nayarit.

Flores de Santiago explained that mangrove forests are typically mapped every five years using remote sensing systems. However, analyzing this data requires high computational capabilities to compare the images. This is where the Google Earth Engine, a new classification tool, proved invaluable. It allowed the researchers to closely examine different types of mangroves using files generated by the European Space Agency's Sentinel II team, which produces a new image every five days.

The researchers took into account the specific seasons in each year, as the intensity of the canopy varies depending on the season. They found a loss of approximately 1,817 hectares of mangrove from 2015 to 2020. The extent of the loss varied by state. For example, in Baja California, where mangroves are isolated and free from human disturbances, the change was minimal. However, in states like Sinaloa, a significant decrease was recorded due to factors such as the expansion of aquaculture and the impact of Hurricane Willa in 2018.

Despite the impact of the hurricane, the team's previous study found that the mangrove canopy gradually recovers. The recent study also noted that in some areas of Sinaloa, aquaculture is expanding, leading to changes in land use and system degradation.

Flores de Santiago concluded that there was more loss than gain in the extent of mangrove forests. While these ecosystems will continue to exist, the services they provide, such as fisheries and carbon storage, can degrade. The research, published in the journal Plos One, aims to assist in decision-making and prioritize resource allocations for blue carbon programs, rehabilitation, and climate change mitigation.