Determining the response of African biota to climate change: using the past to model the future

Prediction of biotic responses to future climate change in tropical Africa tends to be based on two modelling approaches: bioclimatic species envelope models and dynamic vegetation models. Another complementary but underused approach is to examine biotic responses to similar climatic changes in the past as evidenced in fossil and historical records. This paper reviews these records and highlights the information that they provide in terms of understanding the local- and regional-scale responses of African vegetation to future climate change. A key point that emerges is that a move to warmer and wetter conditions in the past resulted in a large increase in biomass and a range distribution of woody plants up to 400–500 km north of its present location, the so-called greening of the Sahara. By contrast, a transition to warmer and drier conditions resulted in a reduction in woody vegetation in many regions and an increase in grass/savanna-dominated landscapes. The rapid rate of climate warming coming into the current interglacial resulted in a dramatic increase in community turnover, but there is little evidence for widespread extinctions. However, huge variation in biotic response in both space and time is apparent with, in some cases, totally different responses to the same climatic driver. This highlights the importance of local features such as soils, topography and also internal biotic factors in determining responses and resilience of the African biota to climate change, information that is difficult to obtain from modelling but is abundant in palaeoecological records.

Measurement of tidal flow using a transit-time ultrasonic breath analyser

The ability of the Transit-time Ultrasonic Breath Analyser (TUBA, GHG Medical Electronics GMBH, Zürich, Switzerland) to measure peak flow and tidal volume in the laboratory was tested using a variety of flow and pressure conditions, chosen to simulate the respiratory patterns of patients receiving mechanical ventilatory support. A stable zero baseline was achieved by acoustic damping of the TUBA flow sensor head. A piston pump was used to generate sinusoidal flow pattern, with a peak flow range from 0.1 to 1.51.s-1. The calculated peak flow matched the peak flow measured by the TUBA. The TUBA accurately measured tidal volumes (+/- 10%) delivered using three different flow patterns over a range of volumes from 0.25 to 11. We conclude, that once modified, the TUBA can provide an accurate measurement of peak flow and tidal volume over a range of values likely to be encountered during mechanical ventilation of the lungs.