Consequences of Early Late-Pleistocene Megadroughts in Tropical Africa

Extremely arid conditions in tropical Africa occurred in several discrete episodes between 135 and 90 ka, as demonstrated by lake core and seismic records from multiple basins [Scholz CA, Johnson TC, Cohen AS, King JW, Peck J, Overpeck JT, Talbot MR, Brown ET, Kalindekafe L,Amoako PYO, et al. (2007) Proc Natl Acad SciUSA104:16416–16421]. This resulted in extraordinarily low lake levels, even in Africa’s deepest lakes.On the basis of well dated paleoecological records from Lake Malawi, which reflect both local and regional conditions, we show that this aridity had severe consequences for terrestrial and aquatic ecosystems. During the most arid phase, there was extremely low pollen production and limited charred-particle deposition, indicating insufficient vegetation to maintain substantial fires, and the Lake Malawi watershed experienced cool, semidesert conditions (<400 mm>/yr precipitation). Fossil and sedimentological data show that Lake Malawi itself, currently 706mdeep, was reduced to an ~125 m deep saline, alkaline, well mixed lake. This episode of aridity was far more extreme than any experienced in the Afrotropics during the Last Glacial Maximum (~35–15 ka). Aridity diminished after 95 ka, lake levels rose erratically, and salinity/alkalinity declined, reaching near-modern conditions after 60 ka. This record of lake levels and changing limnological conditions provides a framework for interpreting the evolution of the Lake Malawi fish and invertebrate species flocks. Moreover, this record, coupled with other regional records of early Late Pleistocene aridity, places new constraints on models of Afrotropical biogeographic refugia and early modern human population expansion into and out of tropical Africa.

THE EFFECT OF INTENSE LIGHT ON BIRD BEHAVIOR AND PHYSIOLOGY

It has been known for centuries that light (photoperiod) is possibly the major environmental stimuli affecting bird behavior and physiology. The length of the light period stimulates the breeding cycle, migration, fat deposition, and molt in most species of birds. Therefore, it is only natural that one would think of using light as a means of bird control. In fact, light has already been used as a bird control; flood-light traps have been used to trap blackbirds (Meanley 1971); Meanley states that 2000-W search lights have been used to alleviate depredation by ducks in rice fields. Pulsing light is already used on aircraft, aircraft hangers and high towers as a means of detourinq birds (Schaefer, 1968). With some positive results already obtained with light as a bird control, the next step is to see if a better light source (the laser) might not have a greater effect. The laser is basically an intense and coherent light with extreme directivity and, thus, might have greater influence on a bird’s behavioral and physiological responses.