The conversation surrounding global warming tends to be rather anthropocentric. When we speak about global warming and its consequences, we focus on ways in which changes in climate will impact human systems. This is understandable, seeing as these are the changes that will affect our lives the most. It is important to realise however, that we are not alone in our dependence on a stable climate. All life-forms, micro- or macroscopic, have been shaped to fit their circumstances through evolution. Over the course of countless generations, descent with modification has continually moulded us to fit the selective pressures of our environment. Climate is no exception in this, with many life-forms being directly connected and adapted to the Earth’s climate in some way, shape, or form. Moreover, throughout evolutionary history, species have adapted to one-another resulting in intricately balanced and interconnected biological systems. Relationships in biological systems are in turn also influenced by their abiotic surroundings, including the local climate. The summation of biotic and abiotic connections in a given area can be described with the oh-so-popular term “ecosystem”. When we consider all the parts that constitute these ecosystems and how they are directly or indirectly connected to the planet’s climate, it becomes apparent that global warming can have far-reaching consequences for them and the species that they encapsulate. In this piece, I will describe an example of how these consequences may manifest themselves.
Phenology denotes the study of plant and animal life cycles, and how they interact with climate. The degree to which species are capable of adapting their life-cycles to climate change varies depending on the relationship between the two. This variance in adaptability can cause relationships between species to break down, with potentially dire consequences for the organisms that depend on- or are controlled by the species involved. In a 2007 study, Post and Forchhammer provide a compelling example of this phenomenon by examining the effects of climate change on the reproductive success on Barren-Ground Caribou (Rangifer tarandus groenlandicus) in West Greenland.
Barren-Ground Caribou are migratory animals that time their migration in accordance with the length of day and night cycles, an adaptation known as photoperiodism. The specific area in their migratory path that coincides with the production of young is known as their calving range. As is the case with other migratory herbivores, Barren-Ground Caribou have evolved such that the time of year in which they migrate to their calving range coincides with the time of year in which resources are the most readily available. For Barren-Ground Caribou, this peak occurs at the start of the plant growth season due to emergent plant tissue offering them the highest nutritional value. By synchronising the production of young with the green-up of species on which they feed, the Caribou maximize their reproductive output as well as the likelihood of survival for their offspring. Over recent years however, climate change has disturbed this relationship.
Contrary to the photoperiodism displayed by the Caribou, the plants on which they rely for nutrition have generally adapted their life-cycle to seasonal temperature variation. Several studies have already documented a shift of plant life-cycles at high latitudes in response to rising global temperatures, with growth season now occurring earlier in the year. The earlier occurrence of plant-growth season, and by extension peak resource availability for Barren-Ground Caribou, poses a problem due to the fact that the Caribou do not base their migratory life-cycles on temperature averages, and have consequently not adapted the timing of their offspring production to the recent climate shift. This phenomenon is known as a trophic mismatch and can have devastating consequences for affected populations. Post and Forchhammer observed a 300% drop in offspring production for Barren-Ground Caribou in Greenland since 1993, accompanied by a marked increase in mortality rates for the remaining offspring. The interconnected nature of species within an ecosystem means that rapid decline in one species can have sweeping effects across biological systems. Predators that prey on the Caribou may be impacted by a sudden drop in food supply, while plants that are usually controlled by them may experience explosive growth, thereby outcompeting other plants. These are just a few examples of how de-synchronization of various species’ life cycles as a consequence of climate change can cause extensive damage to ecosystems.
I’ll be the first to say it: climate change is nothing new. Life on Earth has existed for billions of years and has adapted to changes more drastic than those we are seeing the Anthropocene. With this in mind, there are still two things worth noting:
- While natural systems are capable of adapting to climate change, this adaptation takes time. The speed at which climatic change takes place (which is currently very high) is therefore an important factor in the damage that it can cause to natural systems.
- While natural systems may, given enough time, recover from rapid climatic change, the widespread disappearance of species and subsequent system-collapse could have far-reaching implications for humans around the world. Life will ultimately be fine. For us humans, this is uncertain.
Ecosystems’ immense complexity and unique nature make them unpredictable as far as responses to climate change go. Systems and species will undoubtedly be differentially affected by global warming, and it is important that we are cautious when making grand, sweeping statements about the effects of climate change on ecosystems. Still, it is important to consider how intimately ecosystems and climate are connected. It is important that we are aware of the influence that we can have on the natural world, and thereby, potentially our own.
Post, E., & Forchhammer, M. C. (2007). Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 363(1501), 2369–2375. doi:10.1098/rstb.2007.2207