How does rising atmospheric CO2 affect marine organisms?

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Volume 2 Number 6:  15 March 1999

It's Happened Before…It Can Happen Again: During the 1970s, the United Nations spearheaded a massive international media campaign to warn the world about the occurrence of extreme and widespread desertification in the African Sahel.  Expanding deserts and prolonged droughts were two phrases commonly used in conjunction with video footage showing blowing desert sands or dried mud-caked reservoirs that once held water.  After viewing numerous such images on television sets across the globe, the general public readily accepted the United Nations' claim that desertification was an escalating environmental threat that needed to be confronted.  And in the wake of growing public concern, the UN was able to convince many nations to follow its prescriptions for a cure.  But were they right?  Was the African Sahel really "headed for hell in a handbasket"?

Journal Reviews
Modeling Natural vs. Human-Induced Climate Change: Effects of natural and human-induced changes in climate were calculated for runoff and wheat yield parameters in Europe over the next 50 years.  It was shown that changes in these parameters due to natural climate variability were similar in magnitude to changes predicted to result from anthropogenically-induced climate trends.

North Atlantic Millennial-Scale Oscillations: Deep-sea sediment cores reveal that millennial-scale climate oscillations of the magnitude of the Little Ice Age and the Medieval Warm Period have regularly occurred throughout the last 11,000 years.

Millennial-Scale Climate Oscillations in the North Atlantic: A deep-sea sediment core reveals that climate is more variable during cooler glacial periods than during warmer interglacial periods.

Ecosystem Adaptation to Millennial-Scale Climate Change: A 60,000-year ocean sediment core suggests that "broad segments of the biosphere are well adapted to rapid climate change."

Extraterrestrial Volatiles and Earth's Climate: A new hypothesis is presented that suggests that fluctuations in earth's temperature over geologic time may be the product of the variable receipt of extraterrestrial volatile elements.

Effects of Elevated CO2 on Photosynthesis in two CAM Plants: Phalaenopsis hybrids grown in elevated CO2 for one week displayed net photosynthetic rates that were 82% greater than those manifested by hybrids grown in ambient CO2, indicating that these CAM species will likely benefit from the ongoing rise in the air's CO2 content.

Effects of Elevated CO2 and Water Stress on a C4 Grass: A drought-resistant C4 grass exhibited greater leaf and stem dry masses when grown in elevated, rather than in ambient, CO2 under environmental conditions that induced water stress.  In addition, elevated CO2 reduced transpiration rates, thereby increasing plant water-use efficiencies, particularly when the atmospheric vapor pressure deficit was high and the soil moisture content was low.

Responses of Three Desert Plants to Elevated CO2: Exposure to an atmospheric CO2 concentration of 700 ppm for two and a half months within controlled environment chambers increased the total biomass of two perennial C3 desert shrubs by approximately 62% and that of a perennial C4 desert grass by 25% relative to plants grown at an atmospheric CO2 concentration of 350 ppm.  Elevated CO2 also differentially affected the uptake rates of important soil nutrients by the three species in ways that would tend to maintain ecosystem biodiversity.

No Evidence of Wide Spread Desertification in the West African Sahel: Vegetative groundcover in the Western Sahel, as mapped by satellite imagery, showed no progressive decline from 1980 to 1995.  Likewise, there was no decline in plant productivity in the region, despite extended periods of extreme drought.  Together, these observations indicate that extensive and severe desertification, as announced by the United Nations in the 1970's, has not occurred in this area.

Increased Rain-Use Efficiencies Indicate No Extensive Sahelian Desertification: A slight but steady increase in rain-use efficiency from 1982-1990 in the African Sahel indicates that severe soil degradation and desertification did not occur in this area over this time period.  In fact, plant productivity increased, suggesting that the aerial fertilization effect of increasing atmospheric CO2 concentrations may have positively affected vegetative growth in this arid region.