28 June 2017, The Conversation, The world’s tropical zone is expanding, and Australia should be worried. The Tropics are defined as the area of Earth where the Sun is directly overhead at least once a year — the zone between the Tropics of Cancer and Capricorn. However, tropical climates occur within a larger area about 30 degrees either side of the Equator. Earth’s dry subtropical zones lie adjacent to this broad region. It is here that we find the great warm deserts of the world.Earth’s bulging waistline Earth’s tropical atmosphere is growing in all directions, leading one commentator to cleverly call this Earth’s “bulging waistline”. Since 1979, the planet’s waistline been expanding poleward by 56km to 111km per decade in both hemispheres. Future climate projections suggest this expansion is likely to continue, driven largely by human activities – most notably emissions of greenhouse gases and black carbon, as well as warming in the lower atmosphere and the oceans. If the current rate continues, by 2100 the edge of the new dry subtropical zone would extend from roughly Sydney to Perth. As these dry subtropical zones shift, droughts will worsen and overall less rain will fall in most warm temperate regions. Poleward shifts in the average tracks of tropical and extratropical cyclones are already happening. This is likely to continue as the tropics expand further. As extratropical cyclones move, they shift rain away from temperate regions that historically rely upon winter rainfalls for their agriculture and water security. Researchers have observed that, as climate zones change, animals and plants migrate to keep up. But as biodiversity and ecosystem services are threatened, species that can’t adjust to rapidly changing conditions face extinction. In some biodiversity hotspots – such as the far southwest of Australia – there are no suitable land areas (only oceans) for ecosystems and species to move into to keep pace with warming and drying trends. We are already witnessing an expansion of pests and diseases into regions that were previously climatically unsuitable. This suggests that they will attempt to follow any future poleward shifts in climate zones. Read More here
Tag Archives: Drought
23 May 2017, The Conversation, Australian farmers are adapting to climate change. 2016-17 has been a great year for Australian farmers, with record production, exports and profits. These records have been driven largely by good weather, in particular a wet winter in 2016, which led to exceptional yields for major crops. Unfortunately, these good conditions go very much against the long-term trend. Recent CSIRO modelling suggests that changes in climate have reduced potential Australian wheat yields by around 27% since 1990. While rising temperatures have caused global wheat yields to drop by around 5.5% between 1980 and 2008, the effects in Australia have been larger, as a result of major changes in rain patterns. Declines in winter rainfall in southern Australia have particularly hit major broadacre crops (like wheat, barley and canola) in the key southeastern and southwestern cropping zones. There is strong evidence that these changes are at least partly due to climate change. Climate change is affecting farm productivity A recent study by the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) confirms that changes in climate have had a negative effect on the productivity of cropping farms, particularly in southwestern Australia and southeastern Australia. In general, the drier inland parts of the cropping zone have been more heavily affected, partly because these areas are more sensitive to rainfall decline. Smaller effects have occurred in the wetter zones closer to the coast. Here less rain can have little effect on – and can even improve – crop productivity. Farmers are reacting However, it’s not all bad news. The study finds that Australian farmers are making great strides in adapting to climate change. Much has been written about the fact that farm productivity in Australia has essentially flatlined since the 1990s, after several decades of consistent growth. The ABARES research suggests that changes in climate go some way towards explaining this slowdown. After controlling for climate, there has been relatively strong productivity growth on cropping farms over the past decade. However, while farms have been improving, these gains have been offset by deteriorating conditions. The net result has been stagnant productivity. Read More here
23 February 2017, The Conversation, Australia’s 2016 environment scorecard: rains return but in some cases too late. After several dry years, vegetation across much of Australia received much-needed rains in 2016. But this broad pattern of improvement belies some major environmental damage in parts of the country – particularly in Tasmania, which was scorched by bushfire, the Gulf Coast and Cape York, which missed out on the rains’ return, and on the Great Barrier Reef, which suffered massive coral bleaching. That is the conclusion of our report on Australia’s Environment in 2016, released today. It’s a summary of the state of the nation’s environmental indicators, which we compiled by analysing huge amounts of satellite imagery, ground data, and water and landscape modelling. The report and the accompanying Australia’s Environment Explorer website summarise those data into graphs and plots for 13 environmental indicators. With most data extending back to at least the year 2000, this makes it possible to see how the environment is changing. Read More here
14 February 2017, Think Progress, Sinking from drought, California is now also flooding. After weeks of rain, Northern California’s surface water systems have been pushed to the breaking point, even while the effects of a five-year drought continue to threaten the state’s long-term groundwater supplies. More than 180,000 people were evacuated Sunday afternoon after spillways for the Oroville Dam in Northern California showed signs of possible collapse. The potential flooding comes as California begins to emerge from its historic, drought. But despite the overabundance of water on the surface, drought conditions underground have likely had a permanent impact on the state. Even under the best conditions, it could take half a century for underground reservoirs to refill. Recent analysis from the California Institute of Technology shows that drought — combined with water use — has caused parts of California to sink, perhaps permanently. Some places show up to two feet of subsidence over the past two years. That’s because as surface water from rain and snowmelt has decreased, farmers have been using more groundwater from reservoirs. “Subsidence caused by groundwater pumping in the Central Valley has been a problem for decades,” write the authors of a new study, which uses NASA data to track California’s sinking. Pumping groundwater reduces the support below-ground aquifers give to the surface, causing it to sink. In recent years, that process has been sped up, as California’s drought has reduced the surface water available to farmers. While surface water can come in the form of rain, or snowmelt, groundwater sits in aquifers and is the result of a slow build up of water below ground. Read More here