The article addresses the need, posed by the challenges of sustainable deve
lopment and the changing context at the beginning of the twenty-first centu
ry, for changes in the method and practice of science. The major challenges
for a 'sustainability science' arise from increasing complexity at the ont
ological, epistemological, and political levels, calling for an integrated
science going far beyond an inter-disciplinary style of research. The requi
rement is for the development. adoption, and dissemination of a truly compl
ex-systems scientific research model. Complex socio-ecological systems shar
e a number of fundamental properties that require changes in scientific met
hods, criteria of truth and quality. and conceptual frameworks. These prope
rties include non-linearity, plurality of perspectives, emergence of proper
ties, self-organisation, multiplicity of scales, and irreducible uncertaint
y. Some implications of the analysis are pointed out, in the form of practi
cal recommendations. The authors argue for the involvement of both natural
and social scientists in the investigation of the necessary steps to develo
p a sustainability science.