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Contributo para a gestão das lagoas do EVOA - espaço de visitação e observação de aves e proposta de plano de monitorização
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Abstract(s)
As zonas húmidas são de elevada importância para muitas espécies da avifauna migradora e residente. Um tipo de zona húmida são os estuários, zonas de transição entre ambientes dulçaquícolas e marinhos. Deste modo, trata-se de um ambiente influenciado pelas marés. O estuário do Tejo é uma das zonas húmidas mais importantes de Portugal e da Europa para a avifauna, tanto pela sua extensão, conseguindo albergar grandes números de aves aquáticas, como pela sua localização estratégica na rota migratória do Atlântico-Este. Um dos grupos de aves mais frequentes e de maior abundância no estuário é o das limícolas. Contudo, quando a maré sobe, as zonas de alimentação para estas aves tornam-se inacessíveis. Assim, estas aves têm de procurar outros locais, sendo, então, essencial a existência de zonas próximas que se mantenham acima da linha de preia-mar. Por esta razão, e pelo facto das zonas húmidas serem dos ecossistemas mais ameaçados globalmente devido à pressão humana, uma das medidas utilizadas atualmente é a criação de zonas húmidas artificiais. Zonas deste tipo mostram-se cada vez mais importantes para a avifauna aquática, constituindo habitats supratidais críticos, que são usados para descanso pelas aves que se alimentam nas zonas entre-marés. Alterações nestes locais poderão significar alterações na distribuição e abundância das aves, principalmente quando se trata de alterações das propriedades físico-químicas dos corpos de água, nomeadamente do pH, salinidade, oxigénio dissolvido, temperatura e altura da água. O presente estudo procurou criar e implementar um plano de monitorização destes parâmetros que permita avaliar as interações entre os fatores abióticos acima mencionados e a diversidade e abundância de aves, nas lagoas do EVOA – Espaço de Visitação e Observação de Aves, localizado na Reserva Natural do Estuário do Tejo, contribuindo assim para uma gestão mais eficaz para a avifauna desta área. No âmbito desta proposta de plano de monitorização, foram selecionados 6 pontos de amostragens, 2 por lagoa, onde se efetuou a monitorização dos parâmetros, 2 vezes por semana, de final de dezembro de 2019 a março de 2020. Paralelamente, foram realizadas contagens das aves presentes nas lagoas. Além disso, pretendeu-se avaliar a importância das lagoas do EVOA como zona de refúgio de maré para as aves do estuário, i.e., avaliar se existem diferenças significativas no número de indivíduos nas lagoas consoante a maré no estuário, através da comparação entre os dados de contagens de maré alta com os de maré baixa, obtidos entre 2013 e 2020. Durante as contagens realizadas para este estudo, observou-se um total de 35 espécies de aves aquáticas nas lagoas do EVOA, sendo os grupos mais representados o das limícolas e dos anseriformes, com 14 e 11 espécies, respetivamente. As espécies mais abundantes neste local são a marrequinha-comum Anas crecca, a narceja-comum Gallinago gallinago e o milherango Limosa Limosa. As variáveis estudadas da qualidade da água não se mostraram relacionadas com a diversidade de espécies e número de indivíduos, algo expectável devido ao reduzido tempo de monitorização e reduzida oscilação nos valores obtidos. Ainda, foi possível verificar que o EVOA alberga um maior número de aves durante o período de maré alta no estuário do Tejo, relativamente ao período de maré baixa, confirmando a sua importância como refúgio da avifauna. Estudos deste tipo são importantes para a gestão das zonas húmidas artificiais, pois permitem definir uma situação de referência e assim qualquer alteração ao longo dos anos poderá ser detetada. Algumas dessas alterações poderão significar alteração da biodiversidade local, sendo essencial continuar com o trabalho de monitorização da qualidade da água das lagoas, estendendo-a a outras componentes do sistema (para além das aves). Para tal, o presente estudo propõe um plano de monitorização, para a componente água, comunidade de invertebrados e avifauna aquática.
Wetlands are considered high importance ecosystems for several species of migratory and resident waterbirds. One type of wetland are the estuaries, where exists a connection between freshwater habitats and the marine environment. Thus, it is an environment influenced by the tides. The Tagus estuary it is one of the most important wetlands of Portugal and Europe for waterbirds, both by its extension, housing large numbers of birds, and by its strategic location in the East Atlantic Flyway. One of the most frequent and abundant groups of birds in this estuary is the waders. However, when the tide rises the feeding grounds become inaccessible. Therefore, these birds need alternative sites where they can continue to feed. For this reason, and because wetlands are one of the most threatening ecosystems today due to human pressure, one measure frequently used is the creation of artificial wetlands. These wetlands are increasingly important areas for aquatic avifauna, representing critical supratidal resting habitats for birds that feed in the intertidal zones. Changes in these ecosystems might mean changes in the distribution and abundance of birds, especially when it comes to the physical-chemical parameters of the waterbodies, such as pH, salinity, dissolved oxygen, temperature and water depth. The present study sought to create and implement a monitoring plan that allows assessing the interactions between the mentioned abiotic factors and the diversity and abundance of waterbirds, in the EVOA’s lagoons, in the Natural Reserve of Tagus Estuary, thus contributing to a more effective management for birdlife in this area. It was selected 6 sampling points, 2 for each lagoon, where the monitoring of theses parameters took place, twice a week, from December 2019 to March 2020. Also, bird counts were made. In addition, it was intended to assess the importance of EVOA’s lagoons as tidal refuges for birds, i.e., asses whether there are differences between the high tide numbers of individuals and the low tide ones, by comparing the data of high tide counts with those of low tide, from 2013 to 2020. During the bird counts performed for this study, it was observed 35 species of waterbirds in the lagoons, with the most represented groups being waders and anatids, with 14 and 11 species, respectively. The most abundant species were the common teal Anas crecca, the common snipe Gallinago gallinago and the black-tailed godwit Limosa limosa. The water quality parameters were not relevant for the species diversity and number of individuals, as expected due to the reduced monitoring time. Also, was possible to verify that EVOA hosts a greater number of birds during the high tide period in Tagus estuary, confirming its importance as a refuge site for waterbirds. Studies of this type are important for the management of artificial wetlands, as any significant change in the water bodies over the years could mean changes in biodiversity and it is crucial to continue this monitoring to see how the EVOA’s lagoons are evolving. For this, the present study proposes a monitoring plan for the water, invertebrate community, and aquatic avifauna components.
Wetlands are considered high importance ecosystems for several species of migratory and resident waterbirds. One type of wetland are the estuaries, where exists a connection between freshwater habitats and the marine environment. Thus, it is an environment influenced by the tides. The Tagus estuary it is one of the most important wetlands of Portugal and Europe for waterbirds, both by its extension, housing large numbers of birds, and by its strategic location in the East Atlantic Flyway. One of the most frequent and abundant groups of birds in this estuary is the waders. However, when the tide rises the feeding grounds become inaccessible. Therefore, these birds need alternative sites where they can continue to feed. For this reason, and because wetlands are one of the most threatening ecosystems today due to human pressure, one measure frequently used is the creation of artificial wetlands. These wetlands are increasingly important areas for aquatic avifauna, representing critical supratidal resting habitats for birds that feed in the intertidal zones. Changes in these ecosystems might mean changes in the distribution and abundance of birds, especially when it comes to the physical-chemical parameters of the waterbodies, such as pH, salinity, dissolved oxygen, temperature and water depth. The present study sought to create and implement a monitoring plan that allows assessing the interactions between the mentioned abiotic factors and the diversity and abundance of waterbirds, in the EVOA’s lagoons, in the Natural Reserve of Tagus Estuary, thus contributing to a more effective management for birdlife in this area. It was selected 6 sampling points, 2 for each lagoon, where the monitoring of theses parameters took place, twice a week, from December 2019 to March 2020. Also, bird counts were made. In addition, it was intended to assess the importance of EVOA’s lagoons as tidal refuges for birds, i.e., asses whether there are differences between the high tide numbers of individuals and the low tide ones, by comparing the data of high tide counts with those of low tide, from 2013 to 2020. During the bird counts performed for this study, it was observed 35 species of waterbirds in the lagoons, with the most represented groups being waders and anatids, with 14 and 11 species, respectively. The most abundant species were the common teal Anas crecca, the common snipe Gallinago gallinago and the black-tailed godwit Limosa limosa. The water quality parameters were not relevant for the species diversity and number of individuals, as expected due to the reduced monitoring time. Also, was possible to verify that EVOA hosts a greater number of birds during the high tide period in Tagus estuary, confirming its importance as a refuge site for waterbirds. Studies of this type are important for the management of artificial wetlands, as any significant change in the water bodies over the years could mean changes in biodiversity and it is crucial to continue this monitoring to see how the EVOA’s lagoons are evolving. For this, the present study proposes a monitoring plan for the water, invertebrate community, and aquatic avifauna components.
Description
Relatório de estágio de mestrado em Ecologia e Gestão Ambiental, Universidade de Lisboa, Faculdade de Ciências, 2021
Keywords
Zonas húmidas Refúgio de maré Avifauna aquática Fatores abióticos Qualidade da água Teses de mestrado - 2021