Abstract

ORTIZ-ACOSTA, Sandra E.  and  ARIAS-VALLEJO, Adriana M.. Assessment and mapping of ecosystem services in the arid region of Mexicali, Mexico. Invest. Geog [online]. 2023, n.111, e60714.  Epub Mar 04, 2024. ISSN 2448-7279.  https://doi.org/10.14350/rig.60714.

Although the provision of ecosystem services is critical for life on earth, human activities and land use changes have modified the extent and composition of various ecosystems around the world, resulting in the loss of biodiversity and the services they provide. To understand the capacities of ecosystems to provide their services, assessment and mapping approaches have been developed, including biophysical assessments that link ecosystem service values with land cover and land use data, allowing the visualisation on maps of key areas that need to be maintained to ensure their future provision. Therefore, the objective of this research was to assess and map the potential supply of priority ecosystem services in the arid region of Mexicali, Baja California. To achieve this objective, a regional-scale biophysical assessment was carried out through an adaptation of Burkhard's matrix methodology, based on land use and land cover and expert consultation. The starting point was the selection of land covers from INEGI's land use and vegetation map series VII (2018), which were reclassified into ten land covers that were defined as proxies for the ecosystems to be assessed, including various types of wetlands; nine priority ecosystem services were selected, which included five regulating services, being local climate regulation, water purification, water flow regulation, aquifer recharge and erosion control; two provisioning services, including food supply and fisheries; and two cultural services, recreation and tourism and environmental education. These services were selected by 10 experts who were chosen based on their experience or professional profile related to the management of ecosystems and natural resources in the study area, and their membership of various sectors. With the ten land covers and the nine priority ecosystem services, the matrix was constructed and evaluated by the experts; subsequently the single matrix was obtained, whose values of potential supply of ecosystem services were transferred to three maps of each category (regulation, provisioning and cultural) and one of the total potential supply. The results showed that cultural ecosystem services had the highest potential supply in the arid region studied (from medium-high to maximum potential). It was found that the land covers that constitute some category of wetland were those that presented the greatest total capacity for the potential supply of ecosystem services (medium-high to high potential), mainly for cultural and regulation services; in addition, the Río Hardy wetland is the cover that has the greatest total potential (3.8) to supply ecosystem services and of those with the smallest surface area (0.23%). On the other hand, based on the maps of spatial distribution of ecosystem services, it was observed that 80.8% of the studied area has a medium-low potential supply capacity (1.1 -2), which corresponds to the coverages of microphilous desert scrub and irrigated agriculture. Additionally, to compensate for and reduce the limitations of the matrix methodology, the standard deviation (SD) was calculated and a comparative review with other works was carried out, finding in the SD that 96% of the experts' answers have a medium and high agreement, while the comparison of the potential supply values of this work with those of the literature showed similar trends. These analyses confirmed the validity of the data obtained and the applicability of the matrix approach for the assessment of ecosystem service potentials in the study region. Finally, it was concluded that the matrix methodology for the assessment and mapping of ecosystem services represents a tool that can be applied simply and relatively quickly when limited data are available. Furthermore, the results of this work allowed the identification of key areas with high potential capacity for ecosystem service provision, including remnant wetlands of the Colorado River, which, although their presence is critical in an arid zone context, their area has been reduced due to altered hydrology of the Colorado River Delta in Mexico and changes in land use. In this sense, the information generated constitutes a relevant input for decision makers and policy makers to identify conservation, management and planning actions for these ecosystems present in an arid region and which provide priority ecosystem services. In this way, the present work, with a matrix approach, contributes to the sustainable management and planning of the territory.

Keywords : Arid ecosystems; Burkhard matrix; urban-rural gradient; land cover; Ramsar wetlands.

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