The Water Planet Lecture 21 Global environmental change Yair Rosenthal
Geosphere Land use changes Biomass burning Deforestation Overgrazing and desertification Mining, construction, urban growth
Hydrosphere River damming Acidification of lakes Groundwater contamination Coastal and estuarine pollution Sea level rise Changes in precipitation
Atmosphere The increase in greenhouse gases from fossil fuel burning (global warming) Ozone depletion (CFC’s) Acid rain
Biosphere Perturbation of the natural biogeochemical cycles Ecological changes - destruction of habitats Decrease in biodiversity Genetic contamination of natural species with domesticated/agriculture species Over hunting, fishing etc.
Environmental change
Aswan Dam, Egypt
Nile River discharge before and after the construction of the Aswan Dam
Some facts About 95 percent of Egypt's population lives within 12 miles of the Nile River. Since the dam was completed in 1970: Freshwater discharge decreased by x4 Nutrients input to the Mediterranea Sea declined The fertility of Egypt's farmland has gradually decreased. Today, more than half of Egypt's soil is rated medium to poor. BUT Effects of severe draughts have deminished
Kesterson Reservoir, California Dissolved selenium carried by runoff from the mountains to the alluvial fans where it has been deposited for “ages”. Recently, however, irrigation leaches Se from the soil and flushes it into the reservoir where it reached toxic levels
Mining
Local sewage impacts
Industrial contamination of groundwater aquifers
Acid rain
Acid rain- causes and results
Deforestation and biomass burning
From rainforest to agriculture- clear cutting
Rondonia, Brazil 1975
Rondonia 1986 The “herring bone” pattern
Rondonia 1992
Rondonia 1996
Deforestation in Costa Rica
Desertification susceptibility
Overgrazing in the Sahel
Desertification in North Africa
Rainfall in the Sahel before and after the industrial revolution Draughts promote dust storms