Researchers at the Potsdam Institute for Climate Impact Research have discovered that conscious choice of food can substantially mitigate climate change and that by reducing the consumption of meat and dairy products and improving agricultural practices we could decrease global greenhouse gas emissions substantially. By 2055 the emissions of methane and nitrous oxide from agriculture could be cut by more than eighty percent which is a significant decrease. The results of the modelling study have recently been published in the journal Global Environmental Change and the scientists say that meat and milk really matter.

Reduced consumption of these commodities could decrease the future emissions of nitrous oxide and methane from agriculture to levels below those of 1995. In the past, agricultural emissions of greenhouse gases, mainly methane and nitrous oxide, have increased steadily. In 2005 they accounted for 14 percent of total anthropogenic greenhouse gas emissions. Besides the conscious choice of food on the consumers’ side there are technical mitigation options on the producers’ side to reduce emissions significantly.
The researchers used a global land use model to assess the impact of future changes in food consumption and diet shifts, but also of technological mitigation options on agricultural greenhouse gas emissions up to 2055. The global model combines information on population, income, food demand, and production costs with spatially explicit environmental data on potential crop yields.
The calculations show that global agricultural non-carbon dioxide (non-CO2) emissions increase significantly until 2055 if food energy consumption and diet preferences remain constant at the level of 1995. Taking into account changing dietary preferences towards higher value foods, like meat and milk, associated with higher income, emissions will rise even more. In contrast, reducing the demand for livestock products by 25 percent each decade from 2015 to 2055, leads to lower non-CO2 emissions even compared to 1995.
There are also technological mitigation options to decrease emissions significantly but these technological mitigation options are not as effective as changes in food consumption.
The highest reduction potential could be achieved by a combination of both approaches, the researchers report. Compared to a scenario that takes population growth and an increase in the demand for livestock products into account, emissions of methane and nitrous oxide could be cut by 84 percent in 2055.
However, livestock products are very valuable for nutrition as they contributed globally an average of one third of protein to dietary intakes in 2003. For many poor and undernourished people in the developing world who frequently suffer from protein deficiencies livestock products are important parts of food consumption. In contrast, less meat-oriented diets in the developed regions would have positive health effects, the authors note. Agricultural, non-carbon dioxide non-CO2 greenhouse gas emissions consist mainly of methane and nitrous oxide. Nitrous oxide is about 300 and methane about 20 times more effective in trapping heat in the atmosphere than carbon dioxide. Agricultural emissions originate from the use of synthetic fertilizers on croplands and from flooded rice fields. Because animal products require large amounts of fodder crops, livestock production is connected to higher emissions from fertilizer application. Additional livestock emissions occur due to manure excretion, management and application and methane producing microbes in ruminants’ digestive systems.

This article is adapted from a report provided by Potsdam Institute for Climate Impact Research (PIK).
Reference:
Alexander Popp, Hermann Lotze-Campen, Benjamin Bodirsky. Food consumption, diet shifts and associated non-CO2 greenhouse gases from agricultural production. Global Environmental Change, 2010; 20 (3): 451 DOI: 10.1016/j.gloenvcha.2010.02.001
APA
MLA Potsdam Institute for Climate Impact Research (PIK) (2010, June 29). Conscious choice of food can substantially mitigate climate change, research finds.

Urban Metabolism
It was reported that the concept of ‘urban metabolism’ has existed for decades and views large cities as living entities that consume energy, food, water, and other raw materials, and release wastes. These releases include carbon dioxide, the main greenhouse gas; air pollutants, sewage and other water pollutants; and even excess heat that collects in vast expanses of concrete pavement and stone buildings. Humans directly produce a significant share of this waste, but emissions from industrial, power generation and transportation systems emit the largest quantities of greenhouse gases and other air pollutants. Other urban metabolisers include sewage systems, landfills, domestic pets and pests like rats, which in some cities outnumber people.
During the last five years, this body of knowledge has drawn into sharper focus the hazards of poor air quality in mega cities, not just on the large local populations but also on population centres, agricultural activities and natural ecosystems located downwind from these sprawling areas. Researchers now acknowledge that carbon dioxide and other pollutants in mega cities make them immense drivers of climate change. They impact climate on both a regional and global level because these long-lived greenhouse gases are dispersed around the world.” More than half the world’s population today lives in cities, and the world’s largest urban areas are growing rapidly. The number of mega cities — metropolitan areas with populations exceeding 10 million — has grown from just three in 1975 to about 20 today.

The Culprits
The most highly polluted mega cities are in developing countries. They include Dhaka, Bangladesh; Cairo, Egypt; and Karachi, Pakistan. Some mega cities in less developed regions have recently mounted air quality management campaigns that have resulted in lower levels of pollution; they include Mexico City, Mexico; Beijing, China; Sao Paulo, Brazil; and Buenos Aires, Argentina. Even the cleanest mega cities like Tokyo/Osaka in Japan and New York City and Los Angeles in the United States — all in the developed world — still have serious problems.
The hot weather and frequent atmospheric inversions in southern California, for instance, foster Los Angeles’ legendary smog problem. Mexico City’s high altitude/low latitude location produces high levels of solar ultraviolet radiation that drive photochemical smog production, and the even higher surrounding mountains trap the resulting pollutants in and over the city on most days.
That causes a very serious situation for residents of Mexico City. There are very unhealthy levels of ozone and fine particle pollutants that produce large numbers of premature deaths each year. Studies show that for each increase of 10 micrograms per cubic metre of these particles, you get roughly a 10 percent increase in premature deaths, producing a decrease in average life expectancy of about 0.8 years. Hospital visits, including bronchitis and asthma cases, also rise.

Controlling urban growth key to improving global air quality
Scientists believe that controlling urban growth in the developing world is key to improving the world’s air quality. Urban pollutant levels in poor countries will remain high, with increased emissions expected as the city populations and economic activities increase. Until mega cities are rich enough to devote significant funds to reduce their emissions, two factors will invariably increase the stresses on their environment — increasing vehicular traffic and industrial growth.

California and Mexico reversing the trend
An example of attempts at reversing this trend can be seen in Southern California, which has taken successful action to modify its urban metabolism, pioneering efforts to reduce motor vehicle emissions. Mexico City — unlike most mega cities in less-developed countries — has also taken successful steps to partially address poor air quality. In the past two decades, the Mexican Government has introduced policies to improve air quality, including requiring pollution control devices like catalytic converters on newer vehicles, reducing sulphur levels in petrol and diesel fuel and relocating some large industrial emitters outside the Valley of Mexico. However, in other parts of the world for example the Mega cities in Asia and Africa urgently need to modify their urban metabolism in similar ways with a few fundamental changes such as getting rid of lead in their gasoline. In the developed world, we can institute emissions controls on diesel vehicles, which create hazardous fine particles, and we can also reduce pollution by using more rail-based mass transport or setting up specialized bus routes.”
The urban metabolism model can reveal how developed-world mega cities, such as Tokyo, New York and Los Angeles, have improved their air quality despite a rise in population. The study also assesses how developing-world mega cities are seriously grappling with the problem.

Adapted from materials provided by American Chemical Society.
American Chemical Society (2009, August 18). How Cities Mimic Life:
Mega cities Breathe, Consume Energy, Excrete Wastes And Pollute.

The Yale researchers found that forest ecosystems recovered in 42 years on average, while ocean bottoms recovered in less than 10 years. When examined by disturbance type, ecosystems undergoing multiple, interacting disturbances recovered in 56 years, and those affected by either invasive species, mining, oil spills or trawling recovered in as little as five years. Most ecosystems took longer to recover from human-induced disturbances than from natural events, such as hurricanes.
“The damages to these ecosystems are pretty serious,” said Oswald Schmitz, an ecology professor at the Yale School of Forestry & Environmental Studies and co-author of the meta-analysis with Yale Ph.D. student Holly Jones. “But the message is that if societies choose to become sustainable, ecosystems will recover. It isn’t hopeless.”

The Yale analysis focuses on seven ecosystem types, including marine, forest, terrestrial, freshwater and brackish, and addresses recovery from major anthropogenic disturbances: agriculture, deforestation, eutrophication, invasive species, logging, mining, oil spills, over fishing, power plants and trawling and from the interactions of those disturbances. Major natural disturbances, including hurricanes and cyclones, are also accounted for in the analysis. The researchers analyzed data derived from peer-reviewed studies conducted over the past century that examined the recovery of large ecosystems following the cessation of a disturbance. The studies measured 94 variables that were grouped into three categories: ecosystem function, animal community and plant community. The researchers quantified the recovery of each of the variables in terms of the time it took for them to return to their pre-disturbance state as determined by the expert judgment of each study’s author. The Yale analysis found that 83 studies demonstrated recovery for all variables; 90 reported a mixture of recovered and non-recovered variables; and 67 reported no recovery for any variable. Schmitz said 15 percent of all the ecosystems in the analysis are beyond recovery. Also, 54 percent of the studies that reported no recovery likely did not run long enough to draw definitive conclusions. In addition, the analysis suggests that an ecosystem’s recovery may be independent of its degraded condition. Aquatic systems, the researchers noted, may recover more quickly because species and organisms that inhabit them turn over more rapidly than, for example, forests whose habitats take longer to regenerate after logging or clear-cutting.

They point out that a potential “pitfall” of the analysis is that the ecosystems may have already been in a disturbed state when they were originally examined. Many ecosystems across the globe that have experienced extinctions and other fundamental changes as a result of human activities, combined with the ongoing effects of climate change and pollution, are far removed from their historical, natural pristine state. Thus ecologists measured recovery on the basis of an ecosystem’s more recent condition. The study points out the need for the development of objective criteria to decide when a system has fully recovered.

The researchers said the analysis rebuts speculation that it will take centuries or millennia for degraded ecosystems to recover and justifies an increased effort to restore degraded areas for the benefit of future generations. “Restoration could become a more important tool in the management portfolio of conservation organizations that are entrusted to protect habitats on landscapes,” said Schmitz.

Jones added: “We recognize that humankind has and will continue to actively domesticate nature to meet its own needs. The message of our paper is that recovery is possible and can be rapid for many ecosystems, giving much hope for a transition to sustainable management of global ecosystems.”