Australia’s Dengue Risk: Human Adaptation to Climate Change - Recent Advances and Issues in Environmental Science - page 139

Several Ae. aegypti collection sites occurred well within the two theoretical cold
climate limits. Table 1 details six Ae. aegypti collection sites as examples where the
annual mean temperature and the mean temperature for July (calculated as (mintemp
+ maxtemp)/2) fall below the theoretical values and range from 12.4-15.4°C and 5.2-
7.6°C respectively.

Table 1. Collection sites in NSW that fall below theoretical cool temperature limits.

Site Locality Annual mean temp

("C)

Max/min temp July
("C)

Mean temp July
(0C)

Elevation (M)

98 Breadalbane 12.4 10.3/0.2 5.25 701

116 Culcairn 14.7 11.9/2.2 7.05 221

187 Wagga Wagga 15.4 12.8/2.4 7.6 177

133 Junee 15.1 12.4/2.2 7.3 295

131 Harden 14.3 12.1 / 1.2 6.65 396

189 Wallendbeen 13.9 11.6/1.0 6.3 468

doi:1 0.1371/journal.pntd.0000429.t001

Theoretical Dengue Transmission Limits
Derrick and Bicks [12] suggested that dengue transmission stopped between the 15°C
and 14°C T W isotherm and suggested that a 14.2°C T W annual mean isotherm best ap-
proximated the temperature limit for transmission in the 1926 dengue epidemic. We
applied this isotherm to Australia for the annual mean isotherm (Figure 4A) as well
as the warmest quarter isotherm (summer; December-February, Figure 4B) and the
coldest quarter isotherm (winter; June-August, Figure 4C). These climate limit maps
indicate that if the vector could re-establish itself throughout its former range then
much of northern tropical Australia would be receptive to dengue transmission year
round and transmission would be possible throughout most of Australia during the
summer months.

DISCUSSION
Can the historical distribution of Ae. aegypti in Australia provide an insight into the
potential distribution potential of this mosquito? Using 234 different spatial data points
generated from historical and contemporary collections of Ae. aegypti in Australia, we
developed ecological niche models to hypothesize the potential range expansion of
this mosquito under today's climate and under future climate change scenarios for
2030 and 2050 using OzClim mid sensitivity values that correspond to a global warm-
ing of 2.6°C for a doubling of CO 2 from 280 to 560 ppm [27]. In Australia general
warming estimates are approximately 1.0°C by 2030 and 1.2-2.2°C by 2050, the latter
values being dependent on CO 2 emissions. While rainfall (outside of far north Australia)
is estimated to decrease by 2-5%, southern Australia is projected to encounter a 5%
reduction in rainfall [13]. Our GARP model for current climate suggested that Ae.