Tracking 130 years of coastal wetland reclamation in Ria Formosa, Portugal: Opportunities for conservation and aquaculture

Economic activities in coastal wetlands are often perceived as incompatible with nature conservation. This negative perception stems from the visible impacts resulting from a continuous process of coastal wetland reclamation, as human pressure increases significantly in global coastal areas. The largest coastal wetland area in southern Portugal, the Ria Formosa, shares a similar perception, where current nature protection status often conflicts with the needed economic development. Here we explore how the economic activities influenced the wetland reclamation process in Ria Formosa, addressing namely aquaculture identified as an activity with a significant compatibilization potential. Different datasets were merged in a Geographical Information System, tracking land use change in Ria Formosa wetlands over the last 130 years at decadal intervals. Our results show that since the end of the 19th century nearly 2000 ha of wetlands were converted to anthropic environments, resulting in a 20 % natural area reduction. From 1885 until the mid-20th century, land use policy was influenced by the significant regional seafood preservation industry, with large swaths of wetlands diked, drained and excavated to give place to traditional salt farms. The following economic downturn gave place for the late industrialization of salt farms, further increasing the reclaimed wetland areas, later stalling with the recognition of the environmental importance of Ria Formosa in 1978. Aquaculture only gained momentum in 1980's with the support of European funding, resulting in the conversion of many unproductive diked areas. However, late 20th century and current land use policy shifted to a nature conservation focus, therefore limiting the use of previously reclaimed areas, a challenge that influenced the abandonment of the modified areas. By studying the long-term change of land use in Ria Formosa, we argue that in high conservation value areas new policies should be considered that stimulate the development of an ecosystem approach to economic activities, namely aquaculture, improving simultaneously the regional environmental status and socioeconomic sustainable development.