One of Earth’s most biodiverse habitats lies off the Scottish west coast – but climate change could wipe it out


Heidi Burdett, Heriot-Watt University and Cornelia Simon-Nutbrown, Heriot-Watt University

Maerl beds stud the ocean floor like underwater brambles. They’re pastel pink and, despite their knobbly appearance, made up of a red seaweed. This algae has a limestone skeleton which gives it a complex three-dimensional structure that is quite unlike the slimy seaweeds you may be more familiar with.

In fact, the closest thing to a maerl bed you’ve probably heard of is a coral reef. Like tropical reefs, the seaweeds in maerl beds interlock as they grow, creating nooks and crannies that serve as the perfect home for a huge range of sealife. Maerl beds are one of the world’s most biodiverse habitats, but unlike coral reefs, few people have heard of them and even fewer study them.

Also known as “rhodolith beds”, maerl beds are found in coastal waters all over the world, from the poles to the equator, but pockets of this habitat form European strongholds off Scotland’s west coast and islands. Sadly, our new research has revealed how climate change threatens to destroy much of this natural heritage before its wonders have been brought to light.

A clump of knobbly, pink, coralline seaweed.
A piece of Scottish maerl that is well over 100 years old.
Nick Kamenos, Author provided

Climate change and maerl beds

Maerl grows at a glacial pace – just 0.2 mm per year in Scotland. This makes it difficult for these habitats to respond to rapid changes in water temperature or ocean currents. But these are just the kind of environmental changes that are expected around Scotland over the coming century.

Until recently, scientists had only conducted small-scale experiments on maerl, so we knew very little about how Scotland’s beds would respond to climate change. To overcome this, we developed a computer model that can predict how the multiple changes to Scotland’s climate will affect the distribution of this habitat by 2100.

Astonishingly, even in the best-case scenario, where emissions are rapidly reduced from current levels, we predict that maerl bed distribution will shrink by 38% by the end of the century. If global emissions stick to their current trajectory, we predict a massive 84% decline in maerl bed distribution around Scotland. Without major changes we will likely follow this path, or worse.

Our research tells us that this would be devastating for the flora and fauna that call this habitat home, including commercially important species such as juvenile pollack, hake and scallops.

Scotland’s maerl beds under ‘worst-case’ warming scenario

Two maps comparing maerl bed distribution off the Scottish coast today and in 2100.

Simon-Nutbrown et al. (2020), Author provided

Refuge areas

Only international efforts to rapidly reduce greenhouse gas emissions could improve the situation for Scotland’s maerl beds. But managing the coastal ocean better – with regulation of trawling and pollution – could soften the blow. Since our model found that the rate of habitat decline will be fastest between now and 2050, the need for rapid action is even more urgent.

It’s unrealistic to expect the entire coastal ocean of a country to be placed under strict marine protection. After all, these regions are very valuable to a range of industries and interests, like tourism, shipping and fishing. Where then, should we focus our efforts? Our computer model helps with this too.

We have identified some key areas in which maerl populations are likely to persist in local micro-climates. Here, temperatures are not predicted to rise as much as the surrounding water and changes in waves and currents at the seafloor are expected to be less pronounced. This will allow maerl beds to remain in areas such as Loch Laxford, mainland Orkney and mainland Shetland. Protecting and monitoring these refuge areas could maximise the chances of these habitats surviving for future generations to enjoy.

Seafloor habitat with pink clumps of maerl, rocks and seaweed.
A Scottish maerl bed brimming with life.
Nick Kamenos, Author provided

Knowing where a habitat might continue to thrive in the future is crucial for planning how to manage coastal seas better, and being able to map these areas can help reconcile their protection with other activities. The refuge areas we found will now be considered as priority conservation areas by the Scottish Government.

Climate change is expected to affect maerl beds all around the world, so the computer model we’ve created can now find other areas where they may be able to cling on globally. Conservation can be long, gruelling work, so being able to focus marine protection efforts in areas with the highest chance of survival could help safeguard at least some of this habitat for future generations.The Conversation

Heidi Burdett, Research Fellow, Lyell Centre for Earth and Marine Science and Technology, Heriot-Watt University and Cornelia Simon-Nutbrown, PhD Candidate in Marine Conservation, Heriot-Watt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Australia’s natural history and native species should be on the citizenship test

Thomas M Wilson, Author provided

Thomas M Wilson, University of Western Australia

Australia’s proposed changes to the citizenship test has raised questions about whether you can really evaluate someone’s “Australian values” via a set of exam questions.

But here’s another question not even considered by the test: should Australian citizenship entail a knowledge and appreciation of Australia’s unique wildlife and natural history?

At its heart, this is a question about what it truly means to be an Australian. Some would argue I’m not qualified even to ask it. My ancestors arrived in Perth in 1830 from England and unloaded plenty of inappropriate cultural baggage, including cats, onto the shores of Australia.

Modern Australia is both an ancient land of hundreds of different languages and cultures, and a creation of transplanted Europeans who have sought to establish Western democratic ideals such as freedom of speech. There have also been many waves of economic migrants or those fleeing persecution and violence in their homelands.

With democratic ideals attacked or disregarded in many parts of the world, Australia’s citizenship test aims to ensure new citizens have a shared knowledge of these values and responsibilities. The current test puts a lot of emphasis on knowing about free speech, the constitution, and how parliaments are organised.

But being Australian shouldn’t just mean agreeing with the principles of free speech and deliberative democracy. In 2006, the Australian author William J. Lines published Patriots: Defending Australia’s Natural Heritage. The title presupposes that being Australian is bound up with knowing and appreciating at least a little of Australia’s heritage of unique lifeforms and ecosystems.

My own book, Stepping Off: Rewilding and Belonging in the South West, published in 2017, also champions the idea of embracing the natural environment as part of one’s identity, with a particular focus on Perth and Australia’s southwest corner, an internationally recognised hotspot for unique plants and animals.

An appreciation of Australia

In my book I lament some aspects of the “Britanisation” of this country by my forebears. I also decry the smooth surface that corporate globalisation has more recently smeared over our modern cities.

As a counterbalance to these forces, I suggest other ways of “becoming Australian” that might help us live more gracefully and sustainably on this landscape.

Read more:
Why so many Australian species are yet to be named

What if we asked prospective Australian citizens to know and value the land on which we live, and the living things with which we share it? This might involve knowing facts such as:

  • much of southern Australia is geologically ancient, and broke from Antarctica around 40 million years ago before drifting north alone, evolving thousands of unique species

  • a eucalyptus leaf contains oils that can cause massive explosions in the forest canopy when fires tear through the environment, but which can also be used in kitchen detergents

  • Australia has about 70 species of macropod, of which kangaroos and wallabies are just two examples, and kangaroo meat is more sustainable than beef or lamb because of its low carbon footprint and its softer impact on the landscape compared with hoofed animals

  • a chuditch (or a quoll on the eastern side of the country), is a small carnivorous marsupial that is very friendly, although it’s (sadly) illegal to keep one as a pet.

Do you know a chuditch when you see one?
SJ Bennett/Wikimedia Commons, CC BY-SA

I’m not suggesting throwing the baby out with the bathwater. I appreciate many of the legacies of Western civilisation, including freedom of speech, deliberative democracy, and the rule of law by an independent judiciary. Of course being Australian should mean accepting these central tenets.

Read more:
The new Australian citizenship test: can you really test ‘values’ via multiple choice?

But we should expect new arrivals to our shores — including those whose ancestors have been here for a couple of centuries — to supplement this culture with an understanding and appreciation of land and ecosystem we live in. These values are also more aligned with those of Indigenous Australian cultures.

Being Australian shouldn’t just mean knowing about federation and the ANZACs, mateship and Vegemite. It should also mean knowing at least a little of the plants and animals, stones and clouds, smells and sights, of our wide shared land.The Conversation

Thomas M Wilson, Honorary Research Fellow in Literature and Environment, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.