I already mentioned that, in my opinion, one of the main reason for which people struggle to understand climate change is that many of the consequences are purely ecological. I completely get it, me personally as a biologist I still struggle to completely have a complete view on the matter as well.
My goal is not to teach you a course on ecology, and I’m not even the most appropriate person to do that; what I want to do is to give you a broad idea on some mechanics behind which ecological structures work so that it can become easier to understand what global warming can lead to.
It might sound weird to an outsider listener but ecologists not only have opinions and can state the magnitude of the problem, but they can also give predictive models on what the future will look like from many points of view.
An important concept in ecology is the one of keystone species. In a community (a collection of multiple populations of different species) a species is defined as keystone if, whenever it’s removed from the context, the community collapses or dramatically change in structure. The fact that we are aware of such species (there are many examples in literature) is already alarming: knowing that removing one species only, for whatever reasons, can make a whole community collapse means that we have to be very careful. Of course species are not necessarily very easy to eliminate from its context; only when the context gets weaker and weaker, then the species is vulnerable.
The hardest part of this concept is accepting the idea that we have no clue in how to identify a keystone species. Yep, how do we know if a keystone species is actually one? We remove it from the context and we see if the community changes. This can be done is an experimental setup but it’s not always feasible and many time the role a species can have in its community is very hard to predict. But as far as the real world is concerned, we have really a blurry idea on how that could work.
So far, it may seem very abstract and theoretical, but what I’m suggesting here is that it’s actually rather intuitive. If a species that has a central role on its community (it could be a predator, a pollinator or even a plant) dies, moves or it’s removed in some way then by a chain-reaction mechanism everything falls apart. It’s like removing the basements of a building: without them the whole 5-stories building falls down.
But the process doesn’t have to be that drastic, even small change can have big consequences in the overall picture. Imagine that for any reasons (for example a change in temperature) a plant species can’t germinate on the same soil it germinated the previous year. It doesn’t imply that the species is extinct or dead but just that it may have moved a little north for example (the seed more to the south have gradually stopped growing while the one in the north have grown normally). In the plant-less area now, few birds that usually fed on the fruits of those plants are obliged to migrate in new areas. This would bring consequences not only in the area that they left (for example some predators were feeding on those birds or other plants were relying on those birds for seed dispersal) but especially in the area they will migrate into. Invasive species of this kind are even harder to predict and model as far as the consequences could be.
As you can see, even just considering normal eat-or-be-eat relationships you can have an idea of the many consequences that a movement/extinction/change in behaviour can have on the community structure. What I’m saying here, is that ecological unities are always networks, never straight lines. And these networks can have many links and interactions very hard to understand, predict and interpret. This is actually an extreme simplification of the problem since in a normal network many other factors are taken normally into account: priority effects, trophic levels, risk effects and many more.
To put now a context, climate change can provide infinite perturbations to the systems. The one we were talking about is global warming. A change in 1-2 degrees, like we have seen so far, even without considering how bad it could get in the future, is already enough to alter species distributions, trophic interactions and life history traits of species. And what about all the other consequences such as ocean acidification, dehydration, raising see levels and loss of nutrients? You can imagine how all this taken together gets completely out of control and once the threshold is surpassed, the consequences will roll downhill like a snowball getting worse and worse. This is especially true because the rate at which the change is occurring is very high for an evolutionary scale and the environment can’t adapt in time.
Surprisingly, in contrast with what you might think after reading this, ecological populations, communities and ecosystems are rather resilient to perturbations. In general species have resisted many alterations throughout history and they do all the time every single day. A bad crop yield, a wild fire, a fiery storm and a dry season are not enough to influence a stable and healthy ecosystem. A healthy ecosystem consists of a very biodiverse and complex network: the more the better. So it’s only because we have continuous perturbation from pollution, temperature shifts and more that the structure is changing and in many cases collapsing.
With a given time, ecosystems are very stable, adaptable and proactive, they have been surviving and changing for millions of years according to their own time scale. The problem now is just that we are too fast. That’s why experts are now worried about “slowing down” the process. It will take forever to “stop” it, but we have at least to slow it down, to allow ecological communities to recover and adapt. Then we have to bring it back to where it was, a healthy ecosystem that works for itself as much as it works for us.
I hope now you have a better idea on how global warming can affect communities and ecosystems, after all it’s pretty intuitive. While you think of a way to slow it down, let me tell you another story..