Continuing our investigation of the science of so-called unconventional gas extraction, we turn to Australia where coal seam gas is driving community and environmental concerns.Although fracking is rarely used here (see the latest industry statistics), and the entire vast Great Artesian Basin is unlikely to be depleted (see the image above), some local water supplies have been contaminated by leaks of waste from drilling, for which the companies responsible have received insignificant penalties (see for example in 2011, 2014 and 2015).Gas's usefulness as a low-emission fuel is also thrown into question by fugitive emissions of methane from the majority of wells (according to a federal government study), although health risks from gas leaks are hard to verify (see the Queensland government report of health impacts on the town of Tara).But don't let that get you down too much, as research as shown that optimism and a positive attitude is associated with lower rates of coronary heart disease in both women (2009) and men (2001), less likelihood of death (2004) and better health overall (1988).