Impact of climate change on water resources in Southern Italy

 

 

Franco Ortolani (1); Silvana Pagliuca (2); Valerio Buonomo(1)

 

(1) Dipartimento di Pianificazione e Scienza del Territorio, Università di Napoli Federico II, Napoli, Italy; fortolan@unina.it

(2) ISAFOM, CNR, via Cupa Patacca, Ercolano, Napoli, Italy; pagliuca@ispaim.na.cnr.it

 

 

 

KEY WORDS: climate change, water resources, Southern Italy.

 

 

The main result achieved with geoarchaeological research consists in the identification of cyclicity (period of about 1000 years) of the major climate and environmental changes that have resulted in real environmental crises lasting between 100 and 200 years in the Mediterranean area (figure 1).    There is clearly a close correlation between climatic and environmental changes and solar activity (concurrence of prolonged maxima of solar activity and warm greenhouse effect periods and concurrence of repeated minima of solar activity and cold periods, such as the Little Ice Ages).

 

 

 

Figure 1 - Stratigraphic reconstructions and palaeoclimatic interpretation of sediments accumulating in Italy in the last 2500 years. 2.1: Stratigraphic correlations between southern (A) and northern Italy (B). 1= human impact, climatic and environmental conditions similar to present day; 2= accumulation of alluvial sediments during the Archaic Little Ice Age (2a; 520-350 BC), The Early Medieval Little Ice Age(2b; 500-750 AD), the Little Ice Age (2c; 1500-1850 AD), characterised by a cold-humid climate; 3= accumulation of wind-borne sand during the warm-arid Roman (3a; 150-350 AD) and  Medieval periods (3b; 1000-1300 AD); 4= similar climatic and environmental conditions to current conditions in Sicily. 2.2: Reconstruction of cyclical climatic and environmental conditions characterising the Historical Period in the Mediterranean area. A= typical climatic and environmental conditions of cold-humid periods (Little Ice Ages), characterised by lower temperatures (about 1.5°C less than the present day), more abundant oceanic-type rainfall, intense soil erosion, moderate soil formation activity; B= current climatic and environmental conditions; B1= similar climatic and environmental conditions to present-day (B) developing since 1850 AD, characterised by Mediterranean-type rainfall and very intense soil formation; B2= similar climatic and environmental conditions to present-day, developing after warm-arid periods, characterised by intense soil erosion and moderate soil formation; C= climatic and environmental conditions of the warm-arid periods (Greenhouse Effect Periods) with desert conditions along the coastal areas south of 41°N; NW= prevailing winds from the northern quadrant; SW= prevailing winds from the southern quadrants with an increase in desert dust. 2.3: Climatic interpretation of the geoarchaeological stratigraphy reconstructed in the  Mediterranean area. 1= accumulation of alluvial sediments, cold-humid climate, (a= Archaic Little Ice Age; b= Early Medieval Little Ice Age; c= Little Ice Age); 2= environmental stability and human impact, similar climate to present-day; 3= accumulation of wind-borne sand south of 41°N, warm-arid climate with environmental conditions which may be correlated with those of “Greenhouse Effect” periods in the Warm Roman period (3a) and the Warm Medieval Period (3b); 4= current climatic conditions; GI= Typical geomorphological instability of the periods of climatic transition.

 

 

 

 

Figure 2 - 1500-2002 climatic evolution and forecast for the near future ("Third Millennium Climatic Tongs").

 

 

Figure 3 - Correlation between climatic evolution of the last 500 years and variation in the concentration of atmospheric CO2 from 1750 to today and forecast for the near future (Third Millennium Climatic Tongs).

 

The climatic and environmental data concerning the Warm Medieval Period examined for the Mediterranean area, the results achieved with research into geoenvironmental changes linked to climatic variations of the historical period, especially of the last few centuries, and the various multidisciplinary data obtained with research in various parts of the world, represent a valid frame of reference for assessing and quantifying the changes that will occur at different latitudes during the enhanced Greenhouse Effect of the Third Millennium.

The history of mankind and the environment in the last few millennia highlights a progressive, cyclical climatic and environmental change which is occurring consistently in multicentennial periods (figure 1).

     On the left-hand side of figure 2 we propose the climatic reconstruction of the past 500 years, using instrumental data and those obtained from natural archives (temperatures) and deduced from the flows of the River Rhone (reconstructed rainfall from 1500 to 1995). The variations in rainfall are represented as percentages of current values. On the right-hand side of figure 6 we advance a scenario of changes in temperatures and rainfall on the basis of millennial cyclicity and assuming that climatic evolution occurs with a similar trend to the previous Medieval Warm Period, resulting in environmental conditions linked to the new greenhouse effect that we term “Third Millennium enhanced Greenhouse Effect”.

    Undoubtedly in the last 150 years human activity has resulted in the largest emission into the atmosphere of greenhouse gases (carbon dioxide, methane etc.). Logically, such pollution has to be reduced and international action has to be taken to protect the atmosphere. Clearly, during a natural period of greater solar activity the increase in the greenhouse effect (connected to anthropogenic gases) could contribute to changing the effects of the temperature rise on the Earth’s surface.

    In the left-hand part of figure 3 (graph 2) we propose the increase in atmospheric CO2 concentration in the past 250 years. In the right-hand part of figure 6 the hypothesised trend in climatic variation according to natural cyclicity is correlated with the hypothesised trend in atmospheric CO2 concentration on the basis of variable emission values. Assuming that climate change follows the reconstructed pattern during the medieval Warm Period (graph 1), it is forecast that the further temperature increase will lead the environmental threshold to be exceeded, triggering abundant carbonatic sedimentation in shallow marine waters (figure 2). This scenario, as occurred during the medieval Warm Period, could have an appreciable effect on atmospheric CO2 concentrations, sequestering considerable percentages. The natural environmental balance would occur again at the end of the postulated new period of considerable solar activity. The right-hand side of graph 2 shows that the trend in the CO2 percentage, as anthropogenic emissions are reduced, is similar to that forecast according to the natural evolution of climatic variation (graph 1).

 

Figure 4 - Reconstruction of climatic variation and the variation in renewable water resources from 1884 to today, prediction of expected changes for the next 100 years in coastal zones and inland Apennine areas in the regions of Campania, Molise and Basilicata, characterised by limestone aquifers and chiefly clayey rocks (graphs 1, 2 and 3) and correlation with soil formation, soil erosion and evolution of silicoclastic littorals (graphs 3 and 4).

 

We believe that it is a serious mistake to attribute current climatic changes exclusively to the production of harmful anthropogenic gases; it appears clear that human activity has happened to intensify precisely in the period of natural climatic transition; this concomitance may result in misleading conclusions being drawn by those who fail to appreciate the complexity and cyclicity of climatic and environmental evolution.

Importantly, cyclical climatic variation, as occurred in the past, will result in new environmental conditions along the belts bordering current climatic zones, establishing environmental conditions that will at times be better and at times will be worse than those established with the Little Ice Age. In particular, it will transform into humid areas a large part of the areas which are currently subtropical deserts.

The scientific limitations to the debate on climate change and the consequent inadequacy of international action have caused a major delay in taking responsible steps to "prepare" the environment of the Mediterranean area (e.g. elimination of water waste, treatment and re-use of waste waters, accumulation of run-off into large and small basins, geoenvironmental restoration of littorals, etc.) so as to attenuate the "environmental damage" forecast for the near future when, especially in central-southern Italy, rainfall will fall sharply with a serious impact on freshwater availability on which much of the country’s socio-economic activity is based.

On the basis of scientific data acquired with geoenvironmental research conducted in the Mediterranean basin, it is possible to predict climatic and environmental changes expected in the next 100 years. The most serious environmental changes are expected in coastal areas where a sharp reduction in rainfall and a marked temperature rise are expected, such as to cause climatic desertification (annual rainfall about 200-250 mm). The alluvial aquifers in these belts, according to three-dimensional relationships with confining acquifers, may be naturally fed only by vertical rainfall (e.g. the northern and southern parts of the Sele river plain, the Alento and Bussento plains) or also by feeding from neighbouring limestone aquifers (e.g. the Campanian Plain and Agro Nocerino-Sarnese) in Southern Italy. The most serious water crisis may be forecast on those plains that do not benefit from the feeding of groundwater from limestone aquifers; the sharp reduction in water feeding into coastal aquifers will cause greater salt water intrusion into depressed retrodunal plains with a resulting crisis for agriculture.

 Considerable problems for irrigation, industrial and domestic uses will arise from the serious reduction in renewable water resources that will affect the limestone aquifers (over 50% less).

The serious environmental changes predicted for the next 100 years will result in  regional and interregional social conflict over water uses. Responsible steps should be taken to prevent and reduce damage, including: adequate laws for the social use of water resources and environmental re-balance by defining a "royalty", to be invested in zones from which the resource is extracted, on water extracted and transported elsewhere; interventions to defend and protect aquifers; exploitation of undersea sources; research and identification of strategic groundwater resources; research for artificially recharging aquifers; plans to capitalise on micro-resources for multiple uses; wastewater treatment and re-use; strategic interventions to eliminate aqueduct losses; research into desalination.