The use of changes in small coastal Atlantic brooks in southwestern Europe as indicators of anthropogenic and climatic impacts over the last 400 years

Abstract

Unlike other aquatic continental ecosystems such as lakes, small coastal brooks have not been used as indicators of anthropogenic or climatic impacts. Our study addresses reconstructing the evolution of coastal brooks in the southwest of Spain from the early 17 th century to the end of the 20 th century using fieldwork, remote sensing, historical sources and microrelief.These brooks have had a continuous regression, losing 84.7% of their length since 1630 AD.From the 17 th century to the beginning of the 20 th century, climatic factors were responsible for the filling and siltation of the thalweg of brooks with sandy sediments of eolian origin.The alternation of dry and humid periods during the Little Ice Age in southern Spain favoured the mobilisation of sandy sediments in a process of secondary dunification, which was initiated during the 18 th century and prominent at the end of the Little Ice Age. This process has coincided with a loss of water availability or an increase of aridity in some lakes and lagoons of southwestern Europe at the end of the 19 th century. However, during the second half of the 20 th century, the average annual rate of thalweg regression almost quadrupled to 432.2 m•year -1 mainly due to anthropogenic impacts associated with logging. These changes coincide with the mobilisation of sandy sediment and the erosion of coastal brooks in southwestern Portugal and other continental aquatic ecosystems in southwestern Spain.Therefore, we believe that changes in small coastal brooks can be used as indicators of anthropogenic and climatic impacts and, in the future, as sentinels to study the effects of climatic change just as lakes, reservoirs and rivers are considered.

A review of the Little Ice Age in Andalusia (Southern Spain): results and research challenges

“…The combination of palaeoflood and historical records for obtaining data on floods that occurred during the last thousand years reduces the uncertainties associated with radiocarbon dating (~50 years), and has even allowed the identification of individual events in the sedimentary record Machado et al, 2011). Other example comes from the study of changes of the peat bog areas (Sousa et al, 2013) and coastal brooks (Sousa et al, 2015) in the Doñana Natural Park (Huelva province), which were investigated combining geomorphological tools with historical documents (chronicles, maps) from the 18th and 19th centuries. The results of these studies highlight that, from the beginning of the 17th century to the end of the 20th, the extent of the peat bog areas has been gradually reduced, dating the end of the Lia in Andalusia at the end of the 19th century.…”

Intra‐annual rainfall variability in the Spanish hydrographic basins

“…Thus, the rainfall concentration after a summer period, with poorly developed vegetation, results in greater rainfall erosivity. Several studies have proved how periods of high rainfall irregularity induce clogging processes in the lagoons (Sousa et al, ) and streams in the southwest of Spain (Sousa et al, ) and Portugal (Devereux, ). Alternation of dry and rainy periods, sometimes with the overlapping of human activity that alters the use of soil, has generated periods of greater dynamism in the activity of the layers of quaternary sands of the southwest of Spain (Sousa and García‐Murillo, ; Sousa et al, ), particularly accentuated at the end of the Little Ice Age in western and central Mediterranean areas (Diodato et al, ).…”

Identifying areas of aquatic plant richness in a Mediterranean hotspot to improve the conservation of freshwater ecosystems

“…In addition, land use may also play a role. In south‐western Spain, many areas were uninhabited until the middle of the 20 th century because of the low fertility of the soil and the high risk of malaria; consequently, local flora and fauna were at least partly protected (Sousa, García‐Barrón, García‐Murillo, Vetter, & Morales, ; Sousa, Morales, García‐Barrón, & García‐Murillo, ).…”