Define "chaos". Ecosystems do tend towards equilibrium, unless something happens to end up having a _really great_ advantage selected for (e.g. our interpersonal politics selecting for intelligence) or the environment changes significantly (e.g. climate change, great big asteroid boi, ice age).
Chaos in the sense of instability, of constant change, of randomness. Earlier ecologists like Frederic Clements thought that ecosystems tended towards a stable climax, but this theory has been largely disproven by more rigorous data analysis that shows ecosystems are more influenced by chance of physiological and environmental condition than by competition.
If you're interested in reading more, I found Kricher's "The Balance of Nature" to be a highly engaging read. There's a good retail PDF available from Princeton University Press [0]
