The interaction of fast and slow processes is an integral parr of the sudde
n large shifts that sometimes occur in ecosystems. To study the effects of
slow/fast variables on ecosystems, we used a range of examples from natural
and exploited aquatic and terrestrial systems. So-called catastrophic bifu
rcations in the dynamics of the fast components are at the heart of such dr
amatic shifts. We discuss some of the most important bifurcations and show
how they can be analyzed. Subsequently, we show how the interaction with sl
owly changing variables can be understood from graphs constructed in a simp
le way using the singular perturbation approach.