Mudança espaço-temporal da disponibilidade de serviços ecossistêmicos e adaptação do método de seu valor global para bacias hidrográficas no semiárido cearense

Abstract

Valuing the ecosystem services of a specific region serves as a basis for monitoring and developing public policies for ecosystem conservation, as well as providing easily understandable data to the general public about the importance of ecosystems for human well-being. Areas where exploitation processes encroach upon natural cover warrant special attention through monitoring and oversight. Thus, the aim was to value the ecosystem services in watersheds in the Ceará semiarid region, and later it was observed that there was a need to adjust the valuation model, prompting a methodological adaptation in which the same study area was applied. Initially, global coefficients for valuing ecosystem services were used for the following land cover classes: forest formation; dense caatinga; sparse caatinga; grasses and pastures; cultivated areas; exposed soils; water bodies; and urban centers. For the identification of these classes, satellite images from the MapBiomas land use and occupation collection were used for the years 2011, 2017, and 2021 for the watersheds of the Upper and Middle Jaguaribe and Salgado. Subsequently, an adjustment of the valuation method was carried out by modifying the global coefficients through the participation of experts following the Delphi method, and then the Analytic Hierarchy Process was used to adjust the data obtained from the interviews and calculate weights that served as modulators of the valuation coefficients for semiarid conditions. Changes in land cover directly reflected the estimated value for ecosystem services; therefore, monitoring land cover through land use maps allows for easy valuation of ecosystem services. The use of global valuation coefficients enabled the valuation of ecosystem services, despite the inherent gaps of the method, such as the absence of coefficients for certain covers and ecosystem functions. The use of this method primarily allows for valuing large areas, serving as a basis for the development of socio-environmental policies. Adjusting the coefficients for the conditions of the study area was a necessary measure and proved capable of filling the gaps of the global coefficients. When the coefficient adjustment was applied, there was a reduction in the value of ecosystem services compared to the values calculated using the global coefficients. Comparatively, the application of regional coefficients for the valuation of ecosystem services in the semiarid region enabled the identification of changes in the value scale of the services, as well as in the hierarchy of importance of the ecosystem services compared to the estimates using global coefficients.