The way in which individuals and organisations make decisions and the
criteria used to define a ''good'' decision have been an important are
a of study for a major part of this century. Two aspects of a good dec
ision are: good process (how the decision is made) and good outcome (w
hat acutally happens). Social decision-making affecting the environmen
t may have long-term, large scale consequences that often cannot be ac
curately measured or predicted in advance. Environmental decision-maki
ng is characterised by uncertainty as to what will occur, what the imp
acts will be and what is the chance of occurrence. Decision support ma
y be described as any ''data, information:; expertise and activities''
that assists the decision-maker. Decision support systems combine dec
ision analysis and information modules. A decision support system fram
ework was applied to the management of Lake Ellesmere, a large brackis
h water lake in Canterbury, New Zealand. The lake is recognised as a w
etland of international importance with high cultural and recreational
values. Currently, there is limited understanding of ecological proce
sses in the lake. There is also considerable institutional uncertainty
. As a result of this combination of factors it was determined that th
e use of a ''soft systems'' learning approach to management would be o
f considerable benefit to present and future decision-makers and manag
ers. (C) 1996 Academic Press Limited