Climate change is happening now and affecting the things we love. As part of Show The Love week we are looking at how nature, in particular seas and seabirds around Scotland’s coasts, is being affected. In the first blog Peadar O’Connell looked at exactly what climate change is and why it is such a threat to our much loved wildlife. In this second blog he looks at what impact it is having on our seas.
Show The Love: Our marine environment
The oceans, which cover over 70% of the earth’s surface, play a pivotal role in how the planet deals with climate change. The temperature in the atmosphere has increased on average, by over 1 degree C over the last century, but in contrast, the sea temperature has risen even more quickly. A staggering 93% of the additional heat that has built up due to greenhouse gases since the middle of the 20th century has been absorbed by the sea, as well as a lot of the CO2 that we have emitted.
Fig 1: 2017 was the third warmest year on record after 2016 and 2015. It is the warmest year on record that was not influenced by El Nio (see previous blog).
Credit: https://www.metoffice.gov.uk/research/monitoring/climate/surface-temperature
What this means is that at the moment the oceans are buffering us from the worst impacts of climate change. However, the storage capacity of the oceans for this excess heat and CO2 is not unlimited and arguably, it is in the sea where the impacts of climate change are being felt most acutely. So let’s have a look at how climate change is affecting the marine environment.
Warming seas
Coral reefs, including Scotland’s own cold-water corals are particularly sensitive to changes in temperature. Coral species form a close partnership, called a symbiosis, with algae. These algae find shelter in the corals and in return provide the corals with nutrients as they photosynthesis. If the water warms above a certain level is stresses the corals and they react by ejecting the algae. This leads to coral bleaching, where whole reefs turn white and begin to die. Only a return to more normal temperatures and the return of the algae can reverse this extreme reaction. Given coral reefs are the rainforests of the seas, supporting an incredible diversity of species, this is a huge concern.
The Atlantic Meridional Overturning Circulation or AMOC for short, is the name for the currents that transport water around the Atlantic, it forms part of the great ocean conveyor belt (fig 2). The UK benefits enormously from these currents, as they ensure a relatively mild winter season by transporting warm water from the Gulf of Mexico. If you want examples of what our winters might be like without the gulf stream just think about areas at a similar latitude to Scotland like Labrador in Canada or the Kamchatka Peninsula in eastern Russia.
Credit: https://climate.nasa.gov/vital-signs/carbon-dioxide/
There are fears however, that the recorded slowing of the Gulf Stream over the last few decades might be related to climate change. As can be seen in fig 2 ocean currents are all connected, so any change in one will affect the other flows meaning less mixing of waters in the oceans. Any reduction in ocean mixing would be catastrophic for marine life as this mixing is critical for the marine food chain as it helps transport nutrients. Changes to ocean currents would also have knock on affects for global weather patterns, such as an increase in droughts, storms and flooding. .
Ocean acidification or the “evil twin of climate change”
As well as temperature rise we can also see impacts on the marine environment from acidification. The seas are absorbing over a quarter of the CO2 that we are currently emitting. CO2 reacts with seawater to create carbonic acid. Why is this important? Well because it can have a very significant impact on sealife, especially on animals that create shells like molluscs (mussels, clams, oysters and periwinkles) and corals. Shells are made from calcium carbonate which is easily dissolved in acid. This has knock on effects on the entire food chain in the seas, as these species are important marine food sources, for example eider and other seaducks are dependent on a good supply of shellfish. The rate of acidification in the oceans today is happening at a rate 100 times faster than at any time in the last 55 million years! Worryingly ocean acidification has been linked to each of the five previous mass extinctions that have occurred in earth’s history.
Sea level rise
Sea level rise, particularly combined with increased severity of storms and flooding is a further threat that will be of particular concern to coastal communities (including many of the UK’s largest cities). The average global sea level rise since 1900 equals about 7-8 inches but about half of this has occurred since 1993 and it has been predicted that it could rise by 1-4 feet by 2100 but a rise of up to 8 feet could be on the cards! Even a small rise can have significant impacts when combined with heavy storms and flooding events (both of which are also predicted to continue to increase over the coming years and decades).
RSPB Scotland has been working on coastal realignment projects, for example at our Nigg Bay Nature Reserve on the Cromarty Firth (see video for more), to try and help wildlife and people adapt to rising sea levels in as natural a way as possible. Moving sea defences inland in this way allows areas to be flooded during high tides, creating important habitat for waders, invertebrates and plants while reducing the risk of nearby land and homes flooding. However, this way of using nature to provide us with long-term solutions to the problem of climate change is challenging the decades old practice of reclaiming land from the sea and protecting it with hard sea walls. We are calling for more realignment projects around Scotland to help us adapt to climate change.
Oceans are incredibly complex, dynamic and fragile places – Blue Planet 2 showed this brilliantly. Much of what we know about the future impacts of climate change on our seas are based on models – these will never be perfect as they are only a prediction, however what is worrying is that the changes we are starting to observe are in some cases worse than the models have predicted. The seas and oceans of the future are likely to be a very challenging environments for our native wildlife and difficult places for us to live next to or work in. We need to act now to protect our seas, and ourselves, from the worst impacts of climate change. We need show our politicians that we need strong new action to halt climate change – it can be done. Show the Love this Valentine’s day for the oceans, our wildlife and all that you hold dear. See what you can do here.