Mountains in East Africa: the missing Commonwealth dimension
Mountains play a vital ro˘le in the global ecosystem and economy. They are a source of most of the world's fresh water and many mountain regions possess key sites of biodiversity, while forested areas are both economically and ecologically important. While international agencies variously highlight mountain issues, there is virtually no direct involvement of Commonwealth-based activities, despite the fact that the Commonwealth contains some of the world's most significant mountain areas. In the wake of the 2002 International Year of the Mountains, the author draws on 15 years of studies of the East African Mountains to examine the successes and failures of government policies and international interventions.
Environmental history of East Africa
Allan Hamilton is a well-known specialist on the Quaternary of East Africa and on the vegetation of the montane belt in that part of the world. In this book he provides an overview of his knowledge on the recent vegetation history of Kenya, Tanzania and Uganda, integrating results from various relevant fields of science. The conclusions for East Africa are presented in relation to the climatic and vegetation history in a wider surrounding area and in other parts of the world. Hamilton presents a well-illustrated, detailed review of existing knowledge and clearly exposes the wide gaps of ignorance in this field and this particular geographical region. Following a short introduction on the East African environment the book embarks on an evaluation of the results of the geomorphological and sedimentological studies of periglacial and lake level phenomena. Next, evidence from pollen and analytical and other palaeobotanical studies are presented in detail, and, finally, distributional patterns are taken into the picture. This evidence is drawn together in a concluding overview. In addition, Hamilton draws attention to aspects of dispersal in tropical forest organisms, peat formation in East Africa, the environmental aspects of the long history of man in the area, and in a final chapter, he emphasizes the precarious situation as regards the conservation of the present environment in East Africa. The text is clear throughout and the facts are ably summarized. These qualities, together with the systematic and subject indices, make it a valuable book of reference for those interested in African vegetation.
Vegetation and Climate
Vegetation and climate.-The most recent phase of ecology, which finds expression in attempts to introduce quantitative methods for the investigation of vegetation and of the factors that determine its nature and distribution, has received a notable contribution in a recent volume by LIVINGSTON and SHREVE.9 "The existence, limits, and movements of plant communities are controlled by physical conditions" is stated as a fundamental law of plant geography, and an attempt is made to map the distribution both of various physical factors and of a considerable number of plants and plant communities. Data for the latter are obtained from a variety of sources, and more particularly from SHREVE'S well known map of the vegetation areas of the United States. In fact a generalized form of this map is employed as a basis upon which to display the distribution of climatic factors. In addition to this, ranges of various plant species and groups of species, such as deciduous, microphyllous, and broad-leaved evergreen trees, are delimited. Here emphasis is placed upon the lack of anything like an adequate knowledge of the ecological distribution, based on relative abundance, dominance, or density of stand, of any considerable number of plants even in such a well explored land as our own. A general discussion of the influence of the environment on plant life classifies environmental factors which are important in distribution as: (i) moisture conditions, (2) temperature conditions, (3) light conditions, (4) chemical conditions, (5) mechanical conditions. These are considered in turn. In discussing the supply of water to vegetation the "residual soil moisture content " of the soil is not regarded as a soil constant, in spite of many data tending to prove that within very considerable limits its constancy holds. No mention is made of wilting or hygroscopic coefficients, nor of the notable contributions of such well known investigators as ALWAY, SHULL, KEEN, and Bouyoucos. These omissions constitute the most serious defect in an otherwise admirable and comprehensive volume. The tabulation of the climatological data, used for the construction of the maps, in a form that makes them available for future investigators is highly to be commended. As an example of such accumulations of exact information regarding conditions limiting growth and distribution, the table of frost data may be cited. Here for i803 different stations the altitude, number of years of record, average date of the last frost in spring, and the earliest in the