644 Nature Vol. 274 17 August 1978 is already extensive work on isolation In comparison with the West conilitions rather than the reed (Phragmites including the use of cellulase produced in the universities left much to be australis). Physical damage from boat in the Institute of Plant Physiology desired, and invariably deficiencies traffic rather then eutrophication is a in Shanghai. K. J. Scott (University of were blamed on the iniquities of the likely cause of this change. Brisbane) reported success in the Gang of Four. To fulfil projects of To ornithologists the Broads are division of barley leaf protoplasts using somatic hybridisation and genetic cloesly asosciated with the bittern a special rapid method of isolation and engineering better trained students are (Botaurus stellaris), a reedswamp bird sequential media incubations; and it required. which began recolonisation of the area was exciting to see jn a visit to the The tour also gave the party first­ in 191 l after 50 years during which laboratory of Li Hsiang-Hui in the hand experience of haploid breeding. only three records of breeding exist. Institute of Genetics, Peking, that he Particular mention may be given to Day and Wilson (Brit. Birds 71, 285; was able to obtain division of wheat the work on wheat seen in the Red 1978) have collated information on the leaf protoplasts after isolation by Star and Tung Pei Wang communes expansion of this species in Britain means of Chinese cellulase, and near Peking, on rice at the Chung since that time, but they also have bad incubation in a relatively simple culture Po County Laboratories and Chin news for the Broads. By 1954, 60 pairs medium. Chow, and on maize in the Corn were nesting in Norfolk (about 75% The post-symposium tour took the Research Institute and the Kwangsi of the British breeding population of party to Shanghai, Hangchow, Kweilin, Agricultural University, Nanning. De­ the time) but this was reduced to 27 Nanning and Kwangchow. Visits of velopment of future programmes of pairs by 1970 and to IO pairs in 1976 scientific interest were interspersed transferring nitrogen fixing genes into (about 20% of the birds breeding in with tours of factories, communes, cereals and of somatic hybridisation Britain). botanical and medicinal herb gardens. will be watched with interest. 0 The decline has not been seen in other Br,itish counties. The bittern population of Suffolk has risen by 50% over the same period. It is therefore The Norfolk Broads under pressure unlikely that any non-local factor, such from Peter D. Moore as hard winters, has been involved. Day and Wilson also produce data THE conservation of fresh water habi­ reviewed by George (Trans. Norfolk concerning the density of breeding tats and their associated swamp and Norwich Nat. Soc 24, 41; 1977). He herons (Ardea cinerea) in the Broads. fen vegetation is rendered difficult both describes experiments which are in They declined abruptly following a by the natural process of succession progress using 20-m diameter Lund hard winter in 1962/63 as did the bit­ and by the vulnerability of such ecosys­ tubes which isolate a body of water terns hut they have subsequently tems to human misuse.. The Norfolk and sediment from its surroundings. recovered to their former level. The Broads in eastern England provide a Preliminary results suggest that some bitterns show some recovery, but the good example of how these two forces of the characteristic Broads water general decline in numbers since 1954 can interact to produce an ecological plant species which have recently has continued. headache. declined, such as Potamogeton pecti­ The explanation must lie in a dele­ The open water areas of the Broads natus and Najas marina, germinate terious local factor such as pollution, were themselves produced by Me­ widely but survive only in the tubes. habitat destruction or disturbance. The diaeval peat-cutting and so can be It is not yet clear whether some che­ answer may well lie in the simplified regarded as a man-made environment. mical factor, or turbulence created by food chains resulting from eutrophica­ The value of this series of lakes and boats is involved in their inability to tion and increased turbidity. The bit­ interconnecting rivers for recreation survive. tern, unlike the heron, seems unable has long been recognised, although its Mud sedimentation rates have in­ to cope with such habitat changes. The exploitation is fast increasing; the creased dramatically in the past 30 Broads thus seem to be another classic number of power-boat licences issued years and this can probably be ascribed of conflicting interests-wildlife con­ has risen from 1,250 in 1947 to 9,247 to higher phytoplankton productivity servation and recreation being the two in 1976. Boating interests are naturally resulting from eutrophication. Jackson main opponents. The conventional concerned to maintain open, naviga­ (Trans. Norf. Nor. Nat. Soc. 24, 137; British compromise of partition is an ble waters, but the natural processes 1978) has conducted a survey of the incomplete solution to this kind of of secondary succession have tended to macrophyte flora of the Broads and problem where the Broads are inter­ reduce the open water areas as reed­ has concluded that there has been a connected waterways and where many swamp encroaches. Ellis (The Broads, serious decline in the diversity and of the best wildlife areas, such as Hick­ Collins London, 1965) concluded that abundance of water plants in the area. ling, Horsey and Heigham Sound are the amount of open water in the Much of the eutrophication of the also the most popular sites for sailing. Broads had declined from 1,200 ha in Broads results from sewage treatment Where entire river catchments form 1880 to 700 ha in the 1950s. During plants, but the contribution of agricul­ the basic ecological unit for manage­ the foI!owing decade there was an tural run off and from boats has been ment, sub-division of the waterways increase in open water as a result of considerable. George describes fish kills among the conflicting interests alone the grazing activity of the introduced which have been associated with toxin will not solve the problem. O coypu. The coypu population is now production by phytoplankton compo­ controlled, but no further encroach­ nents and a decline in benthic inverte­ ment by vegetation seems to have taken brate diversity. Chironomid midge Correction place. larvae and tubificid worms have re­ In the article 'Monkeys prefer kin' The current state of the aquatic placed a previously rich fauna. (News and Views 274, 311; 1978) flora and fauna of the Broads has been George also points out that the mar­ Wu and Sackett's work was carried ginal reedswamp, which itself once out with the pig-tailed macaque threatened the survival of open water Peter D. Moore is a Senior Lecturer in (Macacca nemestrina) and not the the Department of Plant Sciences, Kings in the Broads, is now declining. Tus­ rhesus monkey as stated. College, London. sock fen often borders the waters

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