What is the next global change factor?
Our list of global change factors is not complete...
What is a factor of global change? Bernhardt et al. (2017) in their wonderful paper offered a possible definition that resonated with me:
a globally occurring factor (does not have to act everywhere, but must be global in scope);
directly linked to human activity;
affects organisms (note that it doesn’t say how or in which direction, positive or negative).
If you find a better definition, please let me know! Most papers define it just by enumeration of examples.
What is an individual factor is a bit more tricky (a question of individuation), in other words, how do you group things: is it chemical pollution, microplastic pollution, pollution with microplastic fibers, etc. A working answer is probably that if you cannot conceptually distinguish effects of closely related ‘items’, they should be collapsed, as done in our paper on classifying factors of global change.
The list of human-caused environmental change is quite long already: in addition to aspects of climate change, we are talking about elevated atmospheric CO2 concentrations, atmospheric nitrogen deposition, artificial light at night, noise pollution, various forms of chemical pollutants, numerous forms of land use change, invasive species and so on.
Bernhardt et al. made the case for including chemical pollution in the canon of global change factors. This paper really marks a turning point, in my opinion, at least in my thinking about this topic. The paper argues that this topic of chemical pollutants has been traditionally the realm of ecotoxicologists, with ecologists more interested in studying other factors. I think this is definitely changing now.
A few years ago, we argued that microplastic contamination should be regarded as a factor of global change, a notion that appears to be increasingly accepted. This recent addition of microplastic is just one example, and clearly there is more to come in terms of chemical pollution, I’m sure. What are emergent chemical pollutants of global concern? The list here will probably be long, and if new substances emerge, it is likely to grow.
But are there also completely different factors that we have missed so far? Irrespective of what this new factor X is, it will fit into an initial classification scheme of global change factors we put together: it’s going to be physical, chemical or biological in nature (or some mixture of physical and chemical, like microplastic particles).
I really liked the article by Emily Elhacham et al. in Nature that calculates the sum of all human-produced materials (which according to their calculations exceeds living biomass). Perhaps concrete building materials (or concrete dust) are something that could pervasively influence ecosystems?
What other human-made materials or phenomena have we so far not considered? Some suggestions I received on twitter/ mastodon in preparation for this newsletter include:
mercury (Hg) (not necessarily new; see this review)
artificial intelligence (even though I would group this more with human activities that give rise to global change, such as transport, rather than with global change factors per se)
nanomaterials (maybe not so new, but there are always new variants) or materials from additive manufacturing
genetically modified organisms (perhaps also not so new; maybe this is already mostly captured by ‘invasive organisms’)
So: what is your prediction for a new factor of global change?
We have a lot of Hg already cycling in the environment, but i think its cycle isnt particularly accelerating. The review states it rose 1.8%, which is little for any emerging contaminant (another point is that we have neglected it). Anyway, Hg is a tricky element to work with in GCF experiments (easily volatile, accumulative and quite toxic) and it is difficult to analyse. I would also think that dust effects on soils and terrestrial ecosystems may be important, now left to think how to implement a dust treatment (continuous application vs single application, what dust, what size, etc)