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MWII'u Wan/ips
The ecology and management of African wetland vegetation
Geobotany 6
Series Editor
M. J. A. WERGER
The ecology and management of
African wetland vegetation
A botanical account of African swamps and shallow waterbodies
edited by
PATRICK DENNY
1985 DR W. JUNK PUBLISHERS
A MEMBER OF THE KLUWER ACADEMIC PUBLISHERS GROUP
DORDRECHT I BOSTON I LANCASTER
Distributors
for the United States and Canada: Kluwer Boston. Inc., 190 Old
Derby Street. Hingham. MA 02043. USA
for the UK alld Ireland: Kluwer Academic Publishers. MTP
Press Limited. Falcon House. Queen Square, Lancaster LAl
lRN. England
/C)/' all other cOlilllries: Kluwcr Academic Publishers Group.
Distribution Center. P.O. Box 322. 3300 AH Dordrecht. The
Netherlands
Library of Congress Cataloging in Publication Data
Main entry under title:
The Ecology and management of African 'Hetland vegetation.
(Geobotany ; 6)
Bibliography: p.
Includes indexes.
1. Hetland flora--Africa--Ecology. 2. I-Ietland
conservation--Africa. I. Denny, Patrick, 1939-
II. SerieE.
QK381.E26 1985 574.5'26325'096 84-21305
ISBN-13: 978-94-010-8929-6 e-ISBN-13: 978-94-009-5504-2
DOl: 10.1007/978-94-009-5504-2
Copyright
© 19R5 by Dr W. Junk Publishers. Dordrecht
All rights reserved. No part of this publication may be reo
produced. stored in a retrieval system. or transmitted in any
form or by asny means. mechanical. photocopying. recording.
or otherwise. without the prior written permission of the pub·
lishers.
Dr W. Junk Publishers. P.O. Box 163. 3300 AD Dordrccht. The
Netherlands.
The magnitude of the task. A satellite-view of the African Continent.
This picture was transmitted by the European Space Agency"s geostationary weather satellite Meteosat-l at
ll55 GMT on 31 May 1978. stationed over tbe Greenwich meridian attbe equator. Meteosat-1 orbits at 36 (X)O
kilometres above the earth's surface; it remains motionless above a fixed point on the equator and scans the
same ]urge area continuously.
Contents
Frontispiece: The magnitude of thc task. A satellite-view of the African Continent V
Foreword by E. Barton Worthington, e.B.E. IX
Preface by Patrick Denny XI
PART ONE: INTRODUCTION
1. Wetland vegetation and associated plant life-forms
by Patrick Denny
PART TWO: WATER PLANT BIOLOGY AND VEGETATION DYNAMICS
2. Submerged and floating-leaved aquatic macrophytes (euhydrophytes)
by Patrick Denny 19
3. Emergent plants of permanent and seasonally-tlooded wetlands
by Keith Thompson 43
4. Surface-floating aquatic macrophytes
by David S. Mitchell \09
PART THREE: ECOSYSTEM STRUCTURE AND FUNCTIONING
5. The structure and functioning of African euhydrophyte communities. The floating-leaved and
submerged vegetation
by Patrick Denny 125
6. The structure and functioning of African swamps
by Clive Howard-Williams and John J. Gaudet 153
VIII
PART FOUR: PROBLEMS, MANAGEMENT AND CONSERVATION
7. African aquatic weeds and their management
by David S. Mitchell 177
8. The conservation and management of African wetlands
by Clive Howard-Williams and Keith Thompson 203
9. African wetland vegetation - concluding perspective
by David S. Mitchell, Patrick Denny and Clive Howard-Williams 231
PART FIVE: BiBLIOGRAPHY
10. Cross-indexed bibliography of African wetland plants and vegetation
by Keith Thompson, Clive Howard-Williams and David S. Mitchell 237
INDEX
Author index 317
Geographical index 321
Systematic index 329
Subject index 337
Foreword
Interest in the biology of African 'wetlands' was initiated in the last century with the hypothesis that Lake
Tanganyika was once part of a Jurassic sea, and was furthered by Cunnington's expedition at the beginning
of this century which proved that it was not. In the late 1920's, ecological studies, encouraged by the growing
importance of inland fisheries, were started hy British, French and Belgian biologists. Some twenty years
later several government limnological research centres and fishery departments were established in tropical
Africa, and scientific progress was accelerated. Scientific collaboration between the regions south of the
Sahara was started formally in 1951 by the Scientific Council for Africa and stimulated by the International
Biological Programme (1964-74) with its emphasis on biological productivity. Some of its interests were
takcn on by SCOPE which recently selected continental wetlands as a Special Project; hence this book. The
five authors, with-Patrick Denny as editor, have made a very valuable contribution both to science and to thc
management of Africa's natural rcsourccs: thcy have filled a gap in the synthesis of knowledge about Africa's
environments which is long overdue.
The term 'wetland' is used today in several different contexts. For this purpose, it excludes the seas and
large open inland waters. which are too deep for rooted plants, but includes the huge areas of floodplains and
dambos which may change seasonally from standing water to very dry lands. Study of the vegetation, which
has to suffer extremes of ecological tolerance, is important if the norms of wetland environments arc to be
understood, and soundly reasoned management stratcgies are to be taken.
We are led from the general bology and dynamics of different groups of waterplants to the structure and
functions of the ecosystems of which they arc part. Much research in recent years has been devoted to
surface-floating plants, and particularly to thc two exotic species which were accidentally introduced from
Latin America to the African continent - Eichlzomias crassipes and Salvinia l1lolesta. These two have taken
full advantage of man's interference with hydrological regimes in warm climates. Perhaps reservoirs and
canals create ecological niches to which the indigenous Pislia and Azolla are less well suited.
The socio-economie importance of wetlands is slIch that some readers will turn first to the three chapters
concerned with management and conservation. On the debit side, aquatic vegetation interferes with water
flow and drainage: it obstructs transport, fisheries and recreation, and favours water-related diseases; and
competes with cultivated rice. On the credit side, the wetland habitats, which waterplants themselves have
done mueh to create, attract and protect a wide variety of wildlife; they provide grazing and useful plant
products; and supply feeding, breeding and refuge areas for fish of commercial importance. Swamps,
although they lose much water to the atmosphere, also store water and keep rivers flowing during dry
seasons. It is, moreover, remarkable that tropical swamps under natural conditions rate well above
cultivated crops in terms of production capacity, so that they might one day add considerably to supplies of
food and fibre.
