Non-climate extreme events

I am writing this as there are expected temperatures of almost 40 degrees C in Berlin today. Extreme events are definitely a major research topic in global change ecology. It seems extreme events are overwhelmingly known in relation to climate: extreme heat, extreme cold, extreme drought, flooding events, also storms and wildfires.

Are there extreme events in other areas of global change biology? I guess there could be, but thinking of chemical pollution, another major aspect of global change besides climate change, maybe we wouldn’t call this global change, but rather an acute pollution event. Maybe the increased frequency of acute pollution events could itself be a thing worth looking into, I am not sure if there are data for this.

Would we call the sudden explosion of an invasive species an extreme event? It seems this unfolds on a slightly different time scale than the climate events, perhaps. On the other hand, I am sure one would call the covid pandemic an extreme event, similarly other disease outbreaks affecting other animals or plants.

Or how about nutrient pulses from terrestrial environments, arriving in aquatic environments, leading to algal blooms? Or a first rain event after a long dry season, washing accumulated N from nitrogen deposition into the soil profile, creating an N pulse in the soil. Would they be categorized as extreme events?

As in many instances in ecology, it probably hinges on the definition, and a good one is very likely tricky. Do you focus on the driver, like it should exceed a certain historical percentile, or do you zoom in on the impacts. If responses are strongly non-linear, then a comparatively non-massive occurrence in terms of historical trends could lead to massive effects; whereas a massive magnitude of a certain factor might not trigger extreme effects if the system happens to be well buffered, I would imagine.

When it comes to chemical pollution, in global change ecology, the focus is definitely on the baseline increase, and not on pulses. If you work on pulses, and thus very high concentrations, you are perhaps more firmly in the ‘classical’ territory of toxicology.

Could we speak of extreme events in land use change, like when large swaths of a landscape are transformed, like when agricultural land is abandoned or when surfaces are sealed?

Another interesting angle: if climate change events trigger follow-on effects in other anthropogenic drivers: you can for example imagine a flood (extreme event) triggering the massive release of pollutants, leading to sudden pollutant increase in an area. Perhaps there is a case where extreme climate events trigger the invasion of a plant or microbes? Another example: extreme heat events triggering light pollution because human activity shifts to ever later in the day, requiring more light. Do we have a bunch of other examples for this?

I wonder how far the extreme event concept carries, and under which circumstances it would be useful to consider in designing future experiments in global change biology. What do you think? Let me know in the comments :)