WATER & IRRIGATION
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Rethinking Australia’s responses to rising heat and water stress
By Professor R. Quentin Grafton
The world is confronting increased heat and water stress that demands, among other responses, much better collective action in how Australia manages its scarce water resources, especially for agriculture. Accelerated Heating
increase in Atmospheric Evaporative Demand (AED) which increases the rate of plant and soil evapor- ation, especially in low soil-moisture conditions. Greater evaporative demand also increases the frequency and magnitude of droughts. In some cases, an increase in AED alone is sufficient to cause drought even in the absence of a decline in annual precipitation. Further, a sufficiently high enough AED can decrease photosynthesis and, thus, reduce plant growth (Vicente-Serrano et al. 2025). Results published in the journal Nature in June 2025 show a global increase in AED. This is worsen- ing hydrological (less water available), agricultural (reduced social moisture) and ecological (lower stream flows) droughts at a planetary scale (Ge- brechorkos et al. 2025). The Nature authors found that rising AED has increased drought severity globally by about 40% while the areas in drought in the world were 74% greater over the period 2018- 2022, compared to 1981-2017.
According to Berkeley Earth’s analysis, the global mean temperature (land and oceans) in 2024 was estimated to have been 1.62 ± 0.06 °C above the average temper- ature from 1850-1900; the hottest year since modern temperature records began. Because warming is much greater over the land than the sea, the 2024 terrestrial average temperature was estimated to be 2.28 ± 0.12 °C greater than the 1850-1900 average. According to the World Meteorological Organiz- ation (2025), each of the last ten years (2015-2024) were individually the warmest ten years on record. This is primarily a result of rising atmospheric con- centrations of carbon dioxide which are at their highest levels in 800,000 years. Increasing Drought Severity Higher surface air temperatures have multiple im- pacts. One of the key consequences on agriculture is a change in drought severity, primarily due to an
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