Arturo Sousa

CHANGES IN THE WETLANDS OF ANDALUSIA (DOÑANA NATURAL PARK, SW SPAIN) AT THE END OF THE LITTLE ICE AGE

The Little Ice Age is a climatic period still insufficiently known. This ignorance is more marked in the case of Andalusia (southern Spain), where only recent works throw any light on the topic. Our studies, primarily from the perspective of botany and changes in the plant landscape, reveal the effects that this period had in these latitudes, and in particular on the Doñana Natural Park (SW Spain). This work shows an aridization in climatic conditions coinciding with the end of the Little Ice Age. The results corroborate the most recent theses on this period in Spain. Furthermore, the effects on the marsh areas studied lead us to conclude that the interpretation of the Little Ice Age in these southern latitudes should be different to that normally given for more northerly latitudes – much better known and more studied than the Mediterranean regions.

Can place names be used as indicators of landscape changes? Application to the Doñana Natural Park (Spain)

This work broaches the possibility of using place names as indicators of original landscapes that have been much transformed. The reconstruction of landscape elements from place names is commonly disputed because such daring notion is impossible to demonstrate. The present case avoids this by making a preliminary study of changes in the landscape using conventional methods. With the knowledge gained from objective and reliable sources, the possibility is analyzed of whether place names are a reflection of landscape changes taking place over a considerable period of time (the last few centuries). It is concluded that, for the present case study, in natural areas with a high rate of change of land use (Doñana Natural Park), place names indicate not only changes in the landscape, but also how such changes are perceived. In the study area, this is especially clear regarding the fens.

Changes in the Erica ciliaris Loefl. ex L. peat bogs of southwestern Europe from the 17th to the 20th centuries AD

This paper analyses a reconstruction of changes from the 17th to the 20th centuries in peat bogs with Erica ciliaris Loefl. ex L. heathlands in southwestern Europe. The reconstruction is performed by means of a multidisciplinary method based on photointerpretation, the examination of historical sources (documentation and maps), and an analysis of microtopography. Historical sources and aerial photos from 1956 and 1987 have also been used to reconstruct the impacts of anthropic activity. In the study area, Doñana Natural Park (SW Iberian Peninsula), peat bogs currently occupy slightly more than 8% of the area that they covered at the beginning of the 17th century. A parallel analysis of anthropic activity in the area over the last four centuries reveals the key role of humans in the disappearance of these peat bogs. This drastic reduction of peat bog area during the 20th century is due to a lowering of the water-table as a result of the impacts of anthropic activity, primarily the establishment of monocultures of Eucalyptus spp. and Pinus pinea. An earlier lowering of the water-table, before these plantations, is attributable to a process of aridisation associated with post-‘Little Ice Age’ warming. Therefore, the impacts associated with climatic trends are synergistically superimposed on those derived from the intense anthropic activity that occurred during the second half of the 20th century. This synergy resulted in a reduction of the surface occupied by the studied peat bogs and their associated E. ciliaris heathlands by 91.1% in SW Europe.

Past and current trophic development in Lake Ammersee – Alterations in a normal range or possible signals of climate change?

In the past decades, nutrient concentrations in several pre-Alpine lakes in central Europe have increased due to human activity in the catchment area. Here, we examine whether this trend will continue in the future, through our analysis of the development of the trophic status, over a period of 25 years (1984 – 2009), of the pre-Alpine, dimictic tempered Lake Ammersee (South-Eastern Germany). The lake showed signs of an elevated eutrophic status until the 1990s. Immense management activities in the catchment area led to a reduction in the nutrient load in the tributaries. The study of dissolved oxygen, total phosphorus (TP) and chlorophyll-a revealed a substantial improvement in the trophic conditions of the lake. We identified a transition period in the development of trophic levels during the years 1996/1997. Therefore, our investigation is divided into two periods: 1984 –1996 and 1997– 2009. By comparing values during these two periods, we found that the annual mean TP concentrations of the complete water column declined from 18.2 μg l (1984 –1996) to 8.8 μg l (1997–2009). During this period the chlorophyll-a values are in relationship to other trophic variables such as TP, dissolved oxygen and sight depths (R between 0.41 and 0.56). At the same time, during the summer months, the surface temperature in the epilimnion increased (by about 0.8 K per decade), which was approximately in line with the thermal increase (about 0.6 K per decade) in the northern hemisphere (Pearson’s correlation coefficient, omitting 2006, of 0.81). In conclusion, in the case of Lake Ammersee, a decrease in nutrient input has led, most recently (1997– 2009), to a substantial improvement in the trophic state. This improvement is fundamentally a result of measures taken to correct any anthropogenic impact. Nevertheless, we show that the thermal stability of the lake reacts to climate-triggered alterations. Therefore it seems that the impact of recent climate change on trophic conditions will have to be monitored closely

Characterisation of the intra-annual rainfall and its evolution (1837–2010) in the southwest of the Iberian Peninsula

Variability in precipitation affects annual total records and causes instability in rainfall distribution throughout the year. Our aim in this study was to develop a procedure, based on pluviometric centralisation and dispersion parameters, that is able to characterise rainfall distribution throughout a year of precipitation in a unique, condensed and precise manner. This enabled the evolution of intra-annual precipitation from 1837 to 2010 in the southwest of the Iberian Peninsula to be determined. The obtained results showed irregular oscillations of the parameters during the selected period. Specifically, patterns of precipitation in recent decades revealed the following differentiating features: the displacement of the most intense rainy periods in autumn with a consequent decrease in precipitation in spring, and more erratic distribution throughout the year with an increase of the frequency of intra-annual dispersion peaks.

The Historical Distribution of Main Malaria Foci in Spain as Related to Water Bodies

The possible connectivity between the spatial distribution of water bodies suitable for vectors of malaria and endemic malaria foci in Southern Europe is still not well known. Spain was one of the last countries in Western Europe to be declared free of malaria by the World Health Organization (WHO) in 1964. This study combines, by means of a spatial-temporal analysis, the historical data of patients and deceased with the distribution of water bodies where the disease-transmitting mosquitos proliferate. Therefore, data from historical archives with a Geographic Information System (GIS), using the Inverse Distance Weighted (IDW) interpolation method, was analyzed with the aim of identifying regional differences in the distribution of malaria in Spain. The reasons, why the risk of transmission is concentrated in specific regions, are related to worse socioeconomic conditions (Extremadura), the presence of another vector (Anopheles labranchiae) besides A. atroparvus (Levante) or large areas of water bodies in conditions to reproduce theses vectors (La Mancha and Western Andalusia). In the particular case of Western Andalusia, in 1913, the relatively high percentage of 4.73% of the surface, equal to 202362 ha, corresponds to wetlands and other unhealthy water bodies. These wetlands have been reduced as a result of desiccation policies and climate change such as the Little Ice Age and Global Climate Change. The comprehension of the main factors of these wetland changes in the past can help us interpret accurately the future risk of malaria re-emergence in temperate latitudes, since it reveals the crucial role of unhealthy water bodies on the distribution, endemicity and eradication of malaria in southern Europe.

A new methodology for estimating rainfall aggressiveness risk based on daily rainfall records for multi-decennial periods

The temporal irregularity of rainfall, characteristic of a Mediterranean climate, corresponds to the irregularity of the environmental effects on soil. We used aggressiveness as an indicator to quantify the potential environmental impact of rainfall. However, quantifying rainfall aggressiveness is conditioned by the lack of sub-hourly frequency records on which intensity models are based. On the other hand, volume models are characterized by a lack of precision in the treatment of heavy rainfall events because they are based on monthly series. Therefore, in this study, we propose a new methodology for estimating rainfall aggressiveness risk. A new synthesis parameter based on reformulation using daily data of the Modified Fournier and Olivers Precipitation Concentration indices is defined. The weighting of both indices for calculating the aggressiveness risk is established by multiple regression with respect to the local erosion R factor estimated in the last decades. We concluded that the proposed methodology overcomes the previously mentioned limitations of the traditional intensity and volume models and provides accurate information; therefore, it is appropriate for determining potential rainfall impact over long time periods. Specifically, we applied this methodology to the daily rainfall time series from the San Fernando Observatory (1870-2010) in southwest Europe. An interannual aggressiveness risk series was generated, which allowed analysis of its evolution and determination of the temporal variability. The results imply that environmental management can use data from long-term historical series as a reference for decision making.