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- Active or passive recovery? Discussing implications of vegetation diversity in unmanaged salt marshesPublication . Almeida, Diana; Neto, Carlos; Costa, José Carlos
- The impacts of land-use changes on the recovery of saltmarshes in PortugalPublication . Almeida, Diana; Neto, Carlos; Esteves, Luciana S.; Costa, José CarlosHuman-induced land-use changes have resulted in loss and degradation of intertidal environments worldwide. Saltmarsh ecosystem dynamics in Portugal are greatly influenced by historic uses and consequent habitat degradation. This study uses an original approach combining vegetation surveys and spatial analysis of historic maps and aerial photographs to assess the effects of land use changes on saltmarshes in two areas in the Algarve, southern Portugal. Historical maps from c. 1800 and aerial photographs from 1958 to 2010 were analyzed to map saltmarsh ecosystems and quantify land-use changes in the Alvor estuary and Arade River. Between c. 1800 and 2010 more than half of saltmarshes were lost due to dyke building and saltmarsh reclamation for agriculture. In mid-1960s, the abandonment of reclaimed agricultural areas resulted in the recolonization of saltmarsh vegetation, which developed physically separated from natural marshes. In the study area, these saltmarshes naturally evolved into two distinct typologies: (1) enclosed mixed marshes, formed by patches of brackish, freshwater and some invasive species developing due to saline intrusion in areas where dykes have not been breached; and (2) tidally-restored saltmarshes, formed in areas where dyke breaching allows incursion of tides and development of a vegetation structure similar to natural saltmarshes. In Europe, passive (without human intervention) and active (artificially planned) saltmarsh restoration are important mechanisms for voluntary or statutory re-creation of intertidal habitats. Improved understanding of the factors influencing the development of distinct saltmarsh typologies through passive ecosystem recovery can provide new insights to support decision-making concerning intertidal habitat restoration.
- Análise espaço-temporal dos Ecossistemas de SapalPublication . Gutierres, Francisco; Neto, Carlos; Reis, Eusébio; Almeida, Diana; Costa, José Carlos; Godinho-Ferreira, Paulo; APRHEste estudo teve por objectivo a análise da dinâmica espaço-temporal dos ecossistemas de sapal da Reserva Natural do Estuário do Sado. O Estuário do Sado é uma das áreas costeiras onde se antevê que as alterações climáticas possam motivar uma subida significativa do nível do mar. Foram seleccionados sectores com uma maior e menor exposição à ondulação lagunar dominante do Estuário do Sado ('lagoon seiche'). A análise de diferentes coberturas de fotografias aéreas e ortofotomapas, entre 1958 e 2007, com recurso a Tecnologias de Informação Geográfica e Geosimulação (Cadeias de Markov e Autómatos Celulares), permitiu a determinação das taxas de erosão e acreção para os sectores abrigados e expostos à ondulação dominante. Procedeu-se ainda à quantificação e à previsão das alterações ao uso e ocupação do solo, com ênfase nos habitats de sapal baixo e alto. Este trabalho demonstrou que a dinâmica de recuo e as alterações de uso e ocupação do solo são dominantes nos ecossistemas de sapal do Estuário do Sado. Apesar do fenómeno de recuo acelerado dos sapais em todo o Estuário do Sado estar correlacionado com a subida do nível do mar, deve ainda ser considerado o efeito induzido pela ocupação antrópica das margens do Estuário. A abordagem desenvolvida poderá assumir um papel relevante na interpretação das dinâmicas espaciais e temporais dos ecossistemas de sapal, e para a simulação da evolução e reacção do território.
- Landscape metrics applied to formerly reclaimed saltmarshes: a tool to evaluate ecosystem services?Publication . Almeida, Diana; Rocha, Jorge; Neto, Carlos; Arsénio, PedroAnalyses of saltmarsh ecosystem services have been particularly focused on the capacity of mitigating climate change effects to cope with rising sea levels and concerning flood management. Nevertheless, ecosystem stability is vital for accurate service delivery, but land-use changes and coastal erosion are affecting saltmarshes. This provides the background for one of the primary arguments for protecting saltmarshes. Landscape metrics were selected according to shape, complexity, and connectivity parameters, and added to average elevation and distance to the coast, for two years - 1972 and 2010. We developed an equation that measures coastal protection, taking into account the results of PCA and the percentage of explained variation of each component (coastal defence index: ES_CoastDef). Three saltmarshes located in the Algarve region, Portugal, were selected to apply the coastal defence index. Individual patches were analysed according to saltmarsh typologies. Results revealed that every saltmarsh decreased its coastal defence from 1972 to 2010; changes in shape and connectivity metrics affect mostly the index performance. In 1972, natural saltmarshes offered a better coastal defence than the other typologies, but in 2010 formerly reclaimed saltmarshes comprised higher values of coastal defence. Positive evolutions in terms of reclaimed saltmarshes have enabled them to provide coastal defence ecosystem services. Thus, through this index it is possible to outline target coastal defence parameters and design strategies for their conservation and consider ecological restoration.
- The Tróia Peninsula: an Aeolian Sedimentological LegacyPublication . Neto, Carlos; Geraldes, Miguel; Almeida, DianaThe integration of studies from fields, such as geomorphology, palynology, history, archaeology and phytogeography, enables assessing the genesis and evolution of the most prominent Portuguese sand spit—the Tróia Peninsula. Data suggests that the spit has formed from Grimaldian dunes converted into barrier islands during the Holocene transgression, and coalesced by the accumulation of sediments transported by the northbound longshore drift. The Tróia Peninsula is integrated in one of the most important Portuguese natural protected areas. It holds a set of flora and vegetation of paramount relevance towards protection and conservation in accordance with the Natura 2000 Network. Its position acts as a barrier against the Atlantic Ocean, having allowed the development of the Sado estuary lagoon, which contains mud flats and salt marsh ecosystems, habitats for a wide range of flora and fauna, some of which with special protection status. The Tróia Peninsula forms indeed a natural protective barrier for the Natural Reserve of the Sado Estuary. The genesis of the peninsula, discussed in the present work, combined with the fact that it is made up exclusively of sand, make it very vulnerable to environmental changes, including sea level rise.