I Ecology textbook for the Sudan Ómeine van noordwijk, 1984 distributed by: Khartoum University Press, P.O.Box 321, Khartoum, Sudan Ecologische Uitgeverij, Gerard Doustraat 18, Amsterdam, the Netherlands ISBN 90 6224114 X produced on recycled paper by: Grafische Kring Groningen typeset: Zetterij de Boom, Siska printing: Drukkerij Papyrus, Brord, Henk, Oskar, Margreeth, Ronald binding: Binderij Steen/Witlox, Henrik, Nanneke illustrations: Kast Olema Daniel (page 33,36,37, 139, 182, 183) Marja de Vries (page 28,30,31,39,41,44,53,56,59,61,62,65,67, SO, 83, 84,88,89,90,91,94,98,99,103,108,109,118,125,131,149, 151, 158, 172, 176, 181, 187, 179,200,263,273,274, back cover) Joan Looyen (page 8, 47, 48, 96, 137) the author (others) II Foreword This book gives an introduction to basic principles of ecology in a Sudanese context, using local examples. Ecology is presented as a way of thinking about and interpreting one's own environment, which can only be learned by practising, by applying these ideas to one's specific situation. Some people are 'ecologists with their heads', considering ecology to be a purely academic, scientific subject; some are 'ecologists with their hearts', being concerned about the future conditions for life on our planet Earth; others are 'ecologists with their hands', having learned some basic principles of ecology by trial and error in traditional agriculture, fisheries etcetera. Education of 'ecologists in their mind', combining the positive sides of the three approaches mentioned, can be seen as essential for the future of a country such as the Democratic Republic 'of the Sudan, with its large environmental potential for positive development, along with great risks of mis-managing the natural resources. The first half of this book (chapter 1-5) deals with ecology as a biological science, studying the relationships between plants, animals, soil and climate. The second half (chapter 6-9) deals with 'human ecology': use and mis-use of the environment by mankind. These aspects are traditionally 'treated as part of geography or general agriculture, but they build on many of the ideas of the first part. This book has been set up as a textbook for introductory ecology courses in universities, agricultural schools, teacher training institutes, etcetera. It will be important background material for biology and geography teachers at secondary school level. The text consists of two levels: the normal print gives the main line of argument and can be read indepently of the smaller print, which adds further details and more examples. The main text can be used at secondary school level, but does not fully coincide with the present, official school syllabus in the Sudan. I hope some people will take up the challenge of making a simpler version, in both Arabic and English for use as a school textbook, along with updating the official syllabus. So far no textbooks have been available dealing with the subject in a comparable way. The excellent African ecology textbooks for A-level by Ewer and Hall (see references) are III more complete and extensive, but of course they contain few Sudanese examples and have a more experimental, scientific approach. Specific information on the Sudanese environment is scarce, partly out of date and often not easily accessible outside University Libraries. Through is book I have tried to make this information available in a more direct way, adding some results of two year ecology-courses in Juba University. Learning the language of ecology is not possible without some of the jargon and technical terms. These have been avoided where possible, but still, the reader may come across many new terms. Technical terms in bold print are listed in the glossary (chapter 11). A special problem is created by use of the names for plants and animals. Scientific names as such are of limited use in a country where keys for identification are hardly at all available. I have tried give synonyms in local languages where-ever I could find these, but my of them are based on the old flora by Broun and Massey, so they may incorrect. By giving many illustrations in the text and in the appendix I hope confusion about the names will be reduced. Many people have contributed to this book, from the initial conception in September 1980 to the proof edition of December 1981 and to the present version. First of all Dr. Ken Knox, at that time senior lecturer Zoology in Juba University, contributed, as well as three students of the College of Education: Abdelrahim Ahmed Salim, Ismail Ishag and Remigius Idroga. Without many of the students of Juba University this book could never have been written, as they were essential in the teaching/learning experience of blending ecological theory with Sudanese realities. Robert Lubajo, Martin Ring Malek, Abdelrahim Ahmed Salim and Abdelrahim, Ahmed El Khidir deserve special mentioning, as they introduced me to their part of the country and helped in describing the respective examples in is book, as well as becoming friends. Mentioning a few names does not mean that I forgot the many others with whom I shared interesting experiences. Through the Dean of the College of Natural Resources and Environmental Sciences, Dr. Peter Tingwa, I would like to thank the University administration for the interest shown and the encouragement given. 'Excellence and relevance' is the motto of Juba University. I hope is book can contribute to at least the relevance of Sudanese education. Several people gave critical comments after reading the proof edition: my former colleague Mr. David Knox, Mr. Scopas Dima, Dr. H. Breman, Joan Looyen, Maria van Noordwijk and Prof. Stortebeker all helped in improving the text. With several collegues in Khartoum and Gezira University I had fruitfull discussions and I want to thank them for the interest shown. IV Kast Olema Daniel and Marja de Vries prepared the illustrations for the proof edition in a friendly cooperation. Joan Looyen helped considerably in transforming the many illustrations added later, into a presentable form. Siska, Brord, Henk and Henrik of the Grafische Kring Groningen produced the printed version of this book in a cooperative way, for which I want to thank them. Finally the Dutch Ministry of Foreign Affairs, Directorate for development cooperation, through the Dutch Embassy in Khartoum, agreed to donate one thousand copies of this book to universities, schools and libraries in the Sudan. By doing so, they made publication of this book possible. Khartoum University Press and Ecologische Uitgeverij Amsterdam agreed to make the book available in bookshops as well. Of course I remain responsible for all remaining shortcomings. If you want to correspond about these, my address is: c/o Institute for Soil Fertility, Qosterweg 92, Haren (Gr.), the Netherlands. Juba/Groningen September 1980 -December 1983 the author. abbrevations used: A. = Arabic B. = Bari D. = Dinka Sh.= Shilluk Z. = Azande V Contents 1. Ecological zones of the Sudan 1.1 What is ecology .........................................................................1 1.2 Climate .....................................................................................10 1.3 Soils .........................................................................................20 1.4 Ecological zones .......................................................................28 1.5 Suggested practicals ..................................................................29 2. The habitats 2.1 Desert and semi-desert ...............................................................32 2.2 Savanna ....................................................................................34 2.3 River and flood region ................................................................38 2.4 Rain forest and montane zone .....................................................44 2.5 Red Seacoast .............................................................................46 2.6 Suggested practicals ...................................................................49 3. Adaptations 3.1 The need for adaptations .............................................................50 3.2 Temperature, waterbalance and growth rate. ................................52 3.3 Surviving the adverse season ......................................................58 3.4 Defence against attack ................................................................64 3.5 The origin of adaptations ............................................................69 3.6 Suggested practicals ...................................................................73 4. Relations 4.1 Relations through changing the environment ................................74 4.2 Consumption .............................................................................76 4.3 Parasitism ..................................................................................83 4.4 Competition and niche-differentiation ..........................................92 4.5 Mutualism and symbiosis ...........................................................95 4.6 Distribution and abundance ........................................................100 4.7 Suggested practicals ...................................................................103 5. The ecosystem 5.1 The food web ............................................................................105 5.2 Decomposition ...........................................................................106 VI 5.3 The nutrient cycle ......................................................................107