Following on in our climate change series, we have a piece from Anna Taylor, one of our Education Officers, on the impact our changing climate will have on life on earth.
Climate change is the biggest pending disaster the human race has ever faced. But it’s not just humans facing this disaster; other animals and plants are already showing the devastating results of global warming. Over the history of Life on earth there have been 5 events that have been classified as major extinction events. We are now in the sixth. So, if you thought that climate change was a nebulous future problem to be dealt with later, you’d be wrong. We have already changed the ecology on earth thoroughly, with a current extinction rate over 1000 times higher than the natural background rates of the last thousand years. Not only that, but the extinction rate has been rapidly increasing since the industrial revolution.
While it is notoriously difficult to work out extinction rates reliably (because we don’t have a solid number on how many species there are altogether), even the most conservative estimates of species loss are stark warnings of a substantial reduction in the biodiversity of Earth.
There have been previous extinction events that have been caused by global warming. There was a small extinction event at the boundary of the Palaeocene and the Eocene (56 million years ago) caused by a spike in carbon released into the atmosphere. This was a natural phenomenon, not caused by humans at all (humans didn’t even exist then – in fact mammals had only just begun to split from reptiles). 0.2 gigatonnes of Carbon were injected into the atmosphere per year, over 20,000 years. You might be forgiven for thinking, well then, that could be repeating today! We’re off the hook! But not so fast, humans are definitely responsible for the global warming we are experiencing – we release about 10 gigatonnes a year and that doesn’t even include methane, an even stronger (20x more powerful than carbon) greenhouse gas of which 50 gigatonnes are likely to be released by humans over the next several decades.
However, it might be possible to gauge the possible severity of the extinction event by looking at past events like this. For example, the end-Permian extinction was caused by global warming. This is not a good thing. The Permian extinction was the most severe extinction in the history of the Earth, with 96% of marine species becoming extinct (marine species are used as the metric for extinction because their fossil record is much more complete). In this severe case, sustained global warming caused an anoxic event where the seas become oxygen-depleted. Hopefully the current warming won’t go as far as that worst-case scenario, but we are already experiencing severe issues in our oceans such as ocean acidification, sea level rise, disruption of thermohaline flow and more el niño/la niña events (more on these in future articles in this series).
Ocean acidification in particular is a worrying trend at the moment. When there is excess CO2 being released into the atmosphere, the sea tries to balance this by absorbing it. For small quantities of CO2 this isnot a problem and the cycle should continue. However, when CO2 production is at the levels of today’s the carbon dioxide in the ocean becomes a problem. When CO2 is absorbed by water, H2O, carbonic acid is produced (HCO3). As I’m sure you all know, acid is not so good for living things in general, but in particular corals, which are very sensitive animals and host some of the greatest biodiversity in the world. Coral bleaching is a major problem in today’s oceans and occurs when the animals living in the coral die off, leaving behind only the hard calcareous structures that protect the delicate polyps. This then has a knock-on effect on higher levels of biodiversity. Many fish use coral reefs and associated organisms such as sea anemones, as nurseries to raise their young, as protection from predators, and even, in the case of the clownfish, to live in.
Figure 1 May 16, 2013 In this image, global glacial mass loss and area are summarized by regions. The area of the red circles corresponds to the annual glacial mass loss from 2003 to 2009. Glacier mass change estimates are determined from a combination of satellite altimetry (ICESat), satellite gravimetry (GRACE) and in situ field observations as determined by Gardner et al. Light orange halos surrounding red circles show the 95 percent confidence interval in mass change estimates, but can only be seen in regions with large uncertainties.
The area of the green/blue circles depicts total glacier area for each region with the tidewater basin fractions [TW] shown separately in blue. The geographic locations of all glaciers, evident primarily in mountainous regions and high latitudes, are shown in yellow with their area increased to improve visibility.
Sea level rise is caused by the melting of glaciers and the ice caps at the poles of the earth. This causes problems for coastal species (of which humans are definitely one) as the land at the edges of continents, and even potentially low lying inland areas will be flooded. Changes is land use are already an issue for many species; with humans improving natural land for industrial and agricultural use. Land-use changes in general are a double whammy for many species – habitats are being destroyed directly and the type of changes being made contribute to carbon emissions by removing major carbon sinks (forest and unimproved grasslands) and often replacing them with carbon sources (farmland, built environment, roads etc).
So, what will happen if the climate warms the 2-5°C projected over the next century? Not only are weather events likely to get much more extreme, with more flooding, hurricanes and heatwaves, the ranges of many species will have to change dramatically if they survive, and that’s a whole other story. Organisms rely on a number of things to survive in their niche. Food is the first. There needs to be a sustainable and suitable food source that they can access in the area for them to survive. Competition is another. Is there another species in the area that relies on the same food source? They will have to fight it out! Even if both species can coexist, competition makes life harder. Usually though, one species is likely to be outcompeted and die out in the area. Predation is important to consider as well. Are there species in the area that will hunt the species we are looking at? Again, predator and prey numbers need to be in balance for the food chain to thrive. So, if conditions in the environment change, the species will either have to adapt (very few will be able to do so fast enough), die off (many will – pandas are an example of a species that cannot adapt fast enough to changes), or move. Once moved, the species will be in a different niche than it started off with. There will be different plants, so they may not have food. If they do have a suitable food, will there be enough of it to go around? There may already be species relying on this, and if it runs out, all these species and our moved species will die out. If the food situation manages to work out, we still need to take care of competition. There will be a different community of species occupying this new area. Are they territorial? Will they allow the new species to move in or kill them off? And are there enough suitable habitats? Finally, will there be a predator in the new area that will hunt our species? If not, the moved species may come in, take over and wipe out the prey species, which will then wipe out any species that relied on that species initially. But if there is a predator that will eat our species, they will potentially wipe out our species. A balance is hard to achieve without years of adaptation.
Now, this hypothetical journey I have taken you on touches on just some of the problems we and other species face by changing the environment around us to this extent. Species that exist in their niches currently will have to adapt, move or die. None of these options are great, and what we are seeing happening now is that species that are high in the food chain where they are native are moving to north and south to stay in the right temperature range. These non-native species are often invasive, meaning that they cause havoc in the new ecosystem they come to inhabit. Many of these species fought hard to become the top predator in their native range and may outcompete other species in their new range, wiping out native species.
This, however is only possible for species that occupy lower latitudes. Those in the north pole, for example, can’t move to a colder area to stay within their temperature range, so species like polar bears are stuck. Bad news for them.
The organisms that may change range aren’t just the animals and plants of the world. One type of organism that tends to be a very good competitor and can adapt fast to new environments are bacteria. This means that many new diseases are being seen in populations that haven’t had them previously, and these populations may have a lower level of immunity to the new disease, or may not vaccinate against it as standard practice, leaving them vulnerable (antibiotic overuse also feeds into this, but isn’t caused by climate change, so I’ll leave it be… for now). This affects humans of course, but amphibians in particular are currently facing a crisis due to emerging diseases. And I prefer amphibians at this point. They didn’t mess up the earth.
So. The outlook isn’t great…but here’s the good news. We are only at the very beginning of the mass extinction to come – it’s not too late. We still have the power to change this alarming potential future by dramatically overhauling our current system. Industrialism needs to stop (intensive farming and large companies pumping out greenhouse gases by the tonne are the first thing that needs to go). In an adjacent goal, our land use needs to become more ecologically friendly. This will contribute to greenhouse gases being removed from the atmosphere but will also directly help the species at risk, for example, recycling waste instead of sending it to landfill will not only save on energy needed for generation of materials but will reduce methane production by landfill. Something simple like planting wildflowers in an urban area will both reduce carbon and help bees survive directly. There are plenty of initiatives to try and improve our impact on the other species of Earth; Earth Day’s fiftieth anniversary is on the 22nd of April 2020 and their campaign this year focuses on protecting threatened species.
Here’s the other good news. Even if we don’t get our act together and prevent the sixth mass extinction on Earth, there’s hope. Humans might drive themselves to extinction along with many other species, but in the past, it has taken only 5-10 million years for the ecosystem to recover and for more species to evolve, increasing the biodiversity to levels comparable to before the event! (I wonder what the species composition of Earth will look like after humans. I vote amphibians as the next dominant species.) I’ll leave you with some wisdom from a favourite of mine, Jurassic Park: ‘Life finds a way’.