Weather: We must be careful to pick the right climate change measures
Monday, May 4, 2009
The window for action on climate change is very small, which makes it all the more important to ensure that the steps we take really do more good than harm
by HENRY HENGEVELD
Two recent developments have once again placed international action to reduce the risks of climate change back in the news.
First, a number of new scientific studies have concluded that the risks of large and potentially catastrophic changes in our climate – and hence weather – over the next few decades and beyond may be significantly larger than the results of the most recent international science assessment released in 2007 had suggested.
The window of opportunity for starting action to avoid dangerous climate change, the researchers involved suggest, may be very small. To do so, global emissions of greenhouse gases would need to peak and begin to decrease within the next 15 years.
The second development has been the election of an American administration which seems determined to actually do something to reduce these risks. Although some suggest that the emission caps and trading proposed by President Obama and his cohorts will not come close to the objectives noted above, such action does help to get the ball rolling. Until now, our federal and provincial governments in Canada have primarily focused on promoting voluntary measures to reduce emissions, but have dragged their heels over meaningful measures. Both the federal and Ontario governments are now making noises about getting their emission reduction agendas in line with that of the Americans.
However, there are cautionary voices amongst scientists about how we go about reducing the risks of climate change. They warn that, unless such actions are developed within the broader context of global, national and regional development goals, and unless they also address the ability to anticipate and adapt to projected changes in weather, they could do more harm then good.
Take, for example, the push across Europe and North America for the development and use of ethanol and other biofuels from the production of cultivated crops. These are often promoted as green technology, but when we take into account all the energy inputs into the crop production and other environmental effects such as emissions of carbon dioxide and nitrous oxides from the cultivated soils, the net benefit is at best questionable.
While the net impact on greenhouse gas emissions may be slightly positive – that is, the total emissions from producing and burning the biofuels are somewhat less than that from the gasoline or diesel it replaces – there are other environmental impacts of biofuel production to be considered.
The advantage of biofuels becomes much greater if they are produced from crop wastes or perennial crops such as switch grass, rather than cultivated crops. Once the technology is fully developed, biogas production from cellulose fibres promises even greater rewards.
The worst case scenario is the production of biofuels from crops grown on tropical lands which were previously forested, but cleared for crop production. Under these circumstances, there is a large net increase in greenhouse gas emissions.
Research groups have also raised similar cautions about the promotion of measures such as no-till farming, especially if undertaken solely for the purpose of sequestering carbon into soils through biological processes.
Canadian studies indicate that no-till can indeed significantly increase carbon storage in the light soils found across Western Canada. There are also many other reasons for going to no-till in these regions, particularly soil conservation.
The benefits in Central and Eastern Canada, where soils are heavier, are more questionable. In fact, as recent experiments conducted by scientists with Agriculture and Agri-Food Canada (AAFC) at an agricultural research station in Quebec have shown, if no-till is practised in heavy clay soils, the net emissions of greenhouse gases may actually increase.
Researchers found that, over a five-year period, no-till reduced aeration of the heavy clay soils and increased water content. This appears to have led to increased denitrification within the soil, resulting in a significant rise in the release of nitrous oxide (a potent greenhouse gas). In contrast, similar experiments on loam soils found no significant increase in nitrous oxide emissions.
However, there are also many examples of research results demonstrating how changes in farm management practices can simultaneously improve farm productivity and reduce net greenhouse gas emissions. AAFC studies show, for example, that improved feed quality improves milk production in dairy cows – and reduces the generation of methane in cattle rumens. Less belching of such methane means lower greenhouse gas emissions. Another example is the use of anaerobic digesters, which can convert manure into methane-rich biogases to be used to fuel electrical generators, meanwhile reducing the challenges of offensive odours and manure disposal. Working models of such digesters have already been developed in Canada for use with wet hog manure slurries. Research is now underway to develop similar systems that can handle dry cattle manure.
A recent American study suggested that, if used for all dairy cattle manure generated in the United States, such digesters could produce enough biogas to replace as much as 2.4 per cent of the coal used to fire the nation's electrical power plants. This would reduce the total greenhouse emissions from the U.S. electricity sector by almost four per cent.
The best advice, according to risk management researchers, is to pursue efforts to reduce the risks of climate change as part of an integrated strategy which considers the social and economic development objectives as well as other pressures to which any industry or region is exposed.
May our leaders listen! BF
Henry Hengeveld is Emeritus Associate, Science Assessment and Integration Branch/ACSD/MSC, Environment Canada.