As with cryosphere-dominated streams the world over, Alpine glaciers are retreating rapidly. As a glacier retreats progressively, it effectively switches on phototrophic activity. It is therefore not surprising that, for almost 100 years, the process has been construed as a chronosequence; one that, if vaguely, is even referred to in Charles Darwin’s Origin of the Species. However, over the last 40 years, the rate of Alpine glacier recession has increased markedly. In this talk, I will propose the hypothesis that, as a result, time’s arrow is losing its importance.
Glacial forefield extent, & the longitudinal extent of phototrophic activity, is increasing so rapidly that other kinds of gradients in successional processes are becoming evident. These gradients are a function of interactions between glaciological, hydrological & geomorphological processes & the ecosystem engineering effects of those keystone species (such as biofilms) that are able to profit from very rapid environmental amelioration. In proposing this hypothesis, however, it is also becoming increasingly clear that we know very little about core elements of this system, including:
1. how & at what rates do glaciers export the sediment that drives proglacial stream morphodynamics?
2. what are the rates of turnover of stream morphodynamics that drive disturbance frequency?
3. how do stream morphodynamics condition the access to water that is so crucial to the primary colonisers that then ‘engineer’ improved environmental conditions for successional species?
4. how effective are primary colonisers et engineering these environmental conditions?
In this talk, I will illustrate how we are addressing these questions in a coupled natural field experiment, at the Otemma Glacier, Switzerland.