Historical overview of agriculture evolution in Estarreja region over the past 35 years using EO (Earth Observation) approaches

• Autor(a) principal: Rego, Luís Carlos Pereira
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/30956
• topic: Agriculture; Estarreja; Land use and land cover (LULC); Land cover change (LCC); Earth observation; Landsat; NDVI

Agriculture is an activity of historical importance in the municipality of Estarreja (northwestern Portugal). Presently, Estarreja still has a significant proportion of land used for agriculture, with nearly half its total area dedicated to this activity, but that has come under pressure in recent decades. To evaluate the temporal shift of agricultural land cover, different methodologies were applied in this study, using: 1) agricultural land cover change maps, derived from the Carta do Uso e Ocupação do Solo (COS) for 1995, 2007, 2010, and 2015, and classification of Landsat TM/OLI false-colour images, obtained for several dates in 1984 and 2019; 2) analysis of NDVI data derived from Landsat TM/ETM+ imagery between 1984 and 2018, relating it with environmental data of temperature and precipitation. In the time intervals covered by COS and Landsat classified images, a significant loss of about 6-8% of agricultural area is seen, with different impacts on different crops, of which rice fields are the most affected. A map of amplitudes of normalized NDVI variation was obtained, coinciding mostly with negative variations (NDVI decrease), where two main hotspots are seen in agricultural areas. Analysis of environmental variables during the study’s time frame by PCA (Principal Component Analysis) shows the occurrence of extreme events of temperature and precipitation, such as on the 15-Nov-2007 (high precipitation), 12-Aug-2003 (high temperature), 27-Jan-2007 (low temperature and precipitation), and 8-Jan-2009 (low temperature). CCA (Canonical Correspondence Analysis) indicated that the biggest NDVI variations were related to high temperatures in the parish of Pardilhó and high temperatures and/or precipitation in the parishes of Canelas/Fermelã and Salreu. Thus, the biggest NDVI decreases in these areas could be attributed to environmental pressures such as extreme events of temperature (leading to droughts) and precipitation (leading to floods). However, other factors like the salinization of agricultural fields in the interface with the Aveiro lagoon should be considered and explored.