Alien Species and Novel Aquatic Ecosystems: The New Reality

Invasions of natural systems by alien species are a worldwide phenomenon.  The presence of aliens in most ecosystems is a conspicuous demonstration of how much we humans have modified ecosystems, especially aquatic ones.    The new reality is that when the effects of human disturbance are cemented by abundant and diverse alien species, novel ecosystems emerge.  While these new ecosystems have many attributes of the systems they replaced, including some native species,  they typically contain many new species and interactions and can change expectedly, making management difficult.  California and other Mediterranean climate countries are leading the world in the rapid development of novel aquatic ecosystems, which now characterize environments from estuaries to rivers to high mountain lakes (and associated terrestrial systems).  Managers need to recognize this new reality in order to find ways to sustain desirable features of the novel systems, especially remaining native species, while reducing undesirable features (often alien species).  I recommend the Michael Rosenzweig’s reconciliation ecology as a practical approach to living with the new reality.  But this means we must be willing to guide the way in which ecosystems are changing, as illustrated by work on Putah Creek (California), a regulated stream. Guidance involves setting realistic policy goals, understanding basic ecology of the managed systems, and taking into account the needs of diverse segments of society. It also needs managers who are risk takers.