Figure 1.
Range maps of focal species in relation to the Kalahari.
Southern African distribution of A: southern pied babblers and B: common fiscals, in relation to the Kalahari basin. Range maps drawn from South African Bird Atlas Project data [29].
Figure 2.
Locations of weather stations used in this study, in relation to Kalahari and Upper Karoo/Bushmanland biotypes [36].
Figure 3.
Decadal change in heat wave indices, averaged across weather stations.
Effect sizes (averaged slope estimates from trend analyses) and 95% confidence intervals for decadal change in six heat wave indices, averaged across 14 weather stations in the southern Kalahari. Units for the effect sizes vary between the heat wave indices and are indicated on the x-axis to aid comparison of like with like estimates. Heat waves were defined using Tthresh values relevant to common fiscals (black circles) and southern pied babblers (white circles).
Figure 4.
Decadal trends in the number of days Tmax > Tthresh, and in maximum heat wave intensity.
Decadal trends in: the number of days exceeding Tthresh for A: fiscals and B: babblers; and the maximum intensity of heat waves for C: fiscals and D: babblers (degree days). The strongest trends for both indices occurred in the northwest of the study area. Circles denote weather station locations, labelled with the appropriate trend estimate. Circle size is proportional to the strength of the trend (effect size), black circles indicate positive trends, and white circles indicate negative trends. Fiscal distribution is shown in light and dark grey on maps A and C; babbler distribution is shown in light and dark grey on maps B and D [29]. Light grey regions: SABAP1 reporting rates < 70%; dark grey regions: SABAP1 reporting rates > 70% (see text for explanation).
Figure 5.
Rates of warming are highest in already-warm areas.
Relationship between linear trend of days with Tmax > 35.5°C and average number of days with Tmax > 35.5°C, showing the tendency for areas that already experience large numbers of hot days (defined as Tmax > Tthresh) each summer to show more rapid gains in additional hot days under a regime of climate warming than cooler areas. Each data point represents a single weather station used in this study.