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Posts Tagged ‘Australia’

Australian fires 2019/20

January 12th, 2020 No comments

Australia is a very flammable continent, and fires have been occurring there for millions of years. As a consequence, many plants and animals have developed adaptations and strategies to cope with recurrent fires. However, the current fire season in eastern Australia is really very severe, including not only very large fires but also high intensity firestorms. SE Australia has suffered other sever fire seasons in the past (an iconic example is the Black Friday bushfires in 1939). Why is this happening now? Here I’ve compiled key figures that help us to understand it.

In the last few years, Australia has been suffering an increase in temperature; on average, each year is hotter than the previous year (Fig. 1). In fact, 2019 was the warmest years, but also the driest year (with the lowest rainfall) ever recorded. December 2019, when most fires started, was climatically an extreme (Fig. 2). During the December heatwave (Fig. 3) some meteorological station (e.g., Penrith, near Sydney) recorded temperatures over 48oC, and the record of highest average maximum temperature for Australia was broken on two consecutive days (40.7 and 41.9oC  on 17 and 18 Dec, respectively). January 4 was Canberra’s hottest day since records began (44oC). In such extreme weather conditions, ignitions easily become a wildfire (in fact, several of the wildfires started from a dry lightning), and fires spread very quickly in a vegetation that has been in a drought for many months. This generates not only huge areas burned (Fig. 4), but also very hot fires and strong uplift air columns that reach the stratosphere (pyrocumulonimbus). These are called firestorms. Firestorms produce there own winds and spread embers and the fire very fast; they even produce lightnings that generate additional wildfires. Firestorms produce extreme fire behaviour that is beyond the capacity of firefighters. In those fires, as it happens in volcanoes, the smoke reaches the stratosphere and circulates at very long distances (e.g., currently smoke from these fires has already reached South America).

The fire season has not ended yet. The ecological effects of these fires will depend on many factors (spatial variability of fire intensity, previous fires, species, etc…). The size and intensity of these fires suggest that they can have some negative consequences, but it is too early for any quantitative evaluation. Many plants are starting to resprout just few days after the fire, even under those drought conditions; some animals are leaving their hiding places, exploring the burned area, and carcasses are locally abundant suggesting patches of high animal mortality. We’ll see when will the rain come, and how plants and animals will respond. For humans, the consequences are catastrophic (fatalities, destruction of many infrastructures, smoke problems, etc.).

Fig. 1. In Australia, each year is hotter than the previous year, on average. From Australian Bureau of Meteorology
Fig. 2. December 2019 was climatically an extreme, unprecedented in relation to rainfall and temperature. Elaborated with data from Australian Bureau of Meteorology
Fig. 3. Global temperature in December 18th, 2019, as shown by Windy. Note also that part of the differences in temperature are due to the different time zones; i.e., middle of the day in Australia, night time in South America, and early morning in Africa.
Fig. 4. Major fires in south-east Australia by January 10th, 2020 (5,634,000 ha). From @eforestal [update Jan 18th: 6 millions ha]

More information:

Australian Bureau of Meteorology  | @eforestal maphub  | NSW fire service | VIC emergency | Desinformation |

Update (4/2020): For a map of the time-since-fire and fire severity across NSW fires, see: Bradstock et al. 2020, Global Change Biol., doi:10.1111/gcb.15111 (spoiler: most fires burned at relatively low severity!)

How plants survive the harsh environment of Australia

June 1st, 2015 No comments

New book: Groom, P. K., and Lamont, B. B. (2015). Plant Life of Southwestern Australia. Adaptations for Survival. De Gruyter Open

Early explorers described Western Australia as ‘the most barren spot on the face of the earth’. In this book we learn that south-western Australia is one of the world’s biodiversity hotspots – not despite but because of its harsh environment. Nutrient-poor soils, frequent droughts, and recurrent fires, together with adverse fauna interactions (e.g., strong-billed cockatoos, voracious kangaroos, and the lack of efficient pollinating bees and hummingbirds) have made this region the perfect evolutionary scenario for developing a plethora of plant adaptations and assembling an hyperdiverse flora. The authors nicely describe this scenario and offer an impressive wealth of knowledge on the natural history of the region in an attractive book with abundant tables and quality full-colour pictures. One of the strengths of the book is that it brings together both biotic and abiotic factors to explain biodiversity, something uncommon in most specialised books.

Overall this is a must-read book for Australian naturalists but will also be a key reference for international ecologists interested in how plants thrive and evolve in dry, nutrient-poor, fire-prone environments. The lessons learned from this region help us understand evolutionary pathways in other dry regions worldwide.

Groom-Lamont

Australian aboriginal fires preserve biodiversity

July 24th, 2012 1 comment

Traditionally, Australian aboriginal people set fires in their landscape to facilitate hunting. A recent study has compared the landscape and fire history from two regions, one where aboriginal people live in a traditional way and the other where fires are “natural” and caused by lightning [1]. The results show that aborigines generate many small fires that are climate-independent, while lightning generates few large climate-driven fires. Anthropogenic fires are smaller even when climatic conditions cause huge fire in the lightning region. The authors suggest that this climate-buffering effects of aboriginal fires has likely been important for many species that benefit both from fine-grained mosaics of alternating resources and from enhanced protection from large catastrophic fires and the predators that hunt within them. This may explain the coincident decline of many small- to medium-sized mammals in the arid regions of Australia with the cessation of aboriginal hunting and burning. That is, the extinction of the aboriginal life style shifted fire regimes from small fires to large climate-driven fires, in a similar manner to the extinction of rural life styles in the Mediterranean Europe [2], and this shift promoted the extinciton of Australian mammals.

Fire Dreaming, by Malcolm Maloney Jagamarra [from www.aboriginalartcoop.com.au]

References

[1] Bird R.B., Codding B.F., Kauhanen P.G. & Bird D.W. (2012). Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands. PNAS, 109, 10287-10292. [pnas]

[2] Pausas J.G. & Fernández-Muñoz S. (2012). Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Clim. Change, 110, 215-226.  [doi | springer | pdf]