To save these threatened seahorses, we built them 5-star underwater hotels

Two adult seahorses living on the seahorse hotels four months after the hotels were deployed.
Author provided

David Harasti, Southern Cross University; Michael Simpson, University of Sydney; Rebecca L. Morris, University of Melbourne, and Ross Coleman, University of Sydney

Venture beneath the ocean and you’ll see schools of fish and other alien-like species that may take your breath away. But one species in particular is an enigma in the marine world: the shy, elusive seahorse.

Approximately 50 species of seahorse are found worldwide, and Australia’s waters are home to at least 17 of them.

However, seahorses are considered threatened around the world, largely from over-harvesting for traditional Chinese medicines, unintended capture in fish trawl nets, and the loss of natural habitats such as seagrasses and mangroves.

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To help seahorse populations bounce back while their natural habitats recover, we created new artificial habitats, called “seahorse hotels”. Our recent research showed how these hotels gave the Australian endangered White’s seahorse (Hippocampus whitei) – also known as the Sydney seahorse – a safe place to come together and call home.

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Seahorse hotels are magnets for marine growth.

Species under threat

Hippocampus, the entire genus (category) for the species, is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) of Wild Fauna and Flora. This means nations that have signed up to the convention must ensure harvesting seahorses – such as for traditional medicines – is done in a sustainable way.

Unfortunately, the CITES listing hasn’t been enough, and several seahorse species are still experiencing population declines.

Fourteen seahorse species are officially listed as endangered or vulnerable, and these species are considered at risk of becoming extinct in the wild. White’s seahorse is among them. It is one of the two seahorse species listed as globally endangered.

White’s seahorse hiding among sponges.
Author provided

The first Australian seahorse under threat

First discovered in Sydney Harbour, White’s seahorse is native to the east coast of Australia and has been spotted from Hervey Bay in Queensland to the New South Wales south coast.

It grows up to 16 centimetres long and is found in shallow water bays and estuaries, where it lives among its natural habitats of sponges, soft corals and seagrasses. Marine biologists have also shown the species “falls in love” – pairings of males and females mate for life.

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But over the past decade, White’s seahorse populations declined by up to 97% at some sites in Port Stephens. It’s now considered “endangered” under the NSW Fisheries Management Act.

White’s seahorse hiding in their natural soft coral cauliflower habitat.
Author provided

The primary cause is the loss of natural habitats across their range in eastern Australia. In fact, within Port Stephens, more than 90% of soft coral and sponge habitats declined over 10 years at sites where the seahorse was once abundant.

These habitats were destroyed through the installation of boat moorings, anchoring of boats, and the inundation of habitats by sand moving into the Port Stephens estuary.

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A home away from home

We devised seahorse hotels to help reverse the decline in White’s seahorse populations. And we named them so because we considered them to be a temporary residence while their natural habitats recovered.

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The idea was born after we saw discarded or lost commercial fisher traps that, when rediscovered, had become heavily covered in marine growth such as sponges and corals.

These lost traps over time become magnets for marine growth which naturally starts to occur within days. As the growth increases over time, fish and invertebrates would move onto these new artificial homes. A few seahorses were even spotted living on them.

An old discarded fish trap that gave David Harasti the idea to develop seahorse hotels.
Author provided

We built on past research, which had also shown White’s seahorse will use artificial habitats if they were available, such as using protective swimming nets found around Sydney.

After we first deployed our 18 hotels, we found it only took within two months for seahorses to start using them. Over time, the numbers of seahorses using the hotels gradually increased: we recorded at least 64 different individuals over the next 12 months of 2018.

Seahorses hold onto the hotels by curling their long tail around the frame, the algae and the sponges, which holds them in place and stops them from being swept away by the waves and currents. By marking each seahorse with small fluorescent tags inserted just beneath the skin (called elastomer), giving each a unique ID, we’re able to track each seahorse.

A baby seahorse clinging to the hotel after months of marine growth.
Author provided

Seahorse babies

We found some seahorses maintained a strong attachment to the hotels – they were spotted regularly on the monthly surveys. One seahorse was even sighted using the hotels in 12 different surveys.

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What’s more, the seahorse hotels help White’s seahorses breed. We saw this when breeding season began in October, finding that 13 males living in the hotels had become pregnant. This gives us hope for the local population size to increase.

Excitingly, our seahorse hotel study has had international interest too, with more hotels trialling in places like Gibraltar, Greece, the United States, Philippines and Indonesia.

A pregnant male seahorse found living on the seahorse hotels for a few months. Look closely and you can spot the fluorescent orange tag just beneath its skin.
Author provided

While we must do what we can to help conserve the natural habitats of seahorses, we at least know we can use the seahorse hotels to recover these elusive populations. Their success in attracting seahorses and helping them come together to mate seems to follow the simple concept of: “If you build it, they will come!”.

David Harasti, Adjunct assistant professor, Southern Cross University; Michael Simpson, PhD candidate, University of Sydney; Rebecca L. Morris, Research Fellow In Ecological Engineering, University of Melbourne, and Ross Coleman, Professor, University of Sydney

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

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New tools help communities measure and reduce their emissions locally

John Englart/Flickr, CC BY-SA

Stephen Pollard, University of Melbourne

The slogan “What you can measure, you can manage” has become a guiding principle for local climate action. There’s an accounting standard made for this purpose: the Global Protocol for Community-scale Greenhouse Gas Emission Inventories. Free online CO₂ emissions snapshots for municipalities in Australia, recently launched by Ironbark Sustainability and Beyond Zero Emissions, make the protocol more accessible than ever for local governments and communities that want to know what their emissions are, and what to do about them.

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The Greenhouse Gas Protocol provides a way to measure local greenhouse gas emissions and removals. It is designed to record two elements of local emissions:

• emissions within a municipal area, such as from cooking with natural gas or driving a car
• emissions from activities within that area that produce emissions somewhere else, such as using electricity from a coal-fired power station or sending rubbish to landfill.

The method creates a consistent approach to measure emissions in different localities. It lets local governments and communities aggregate their individual commitments to reduce emissions.

The protocol is aligned with the Intergovernmental Panel on Climate Change (IPCC) standards that guide countries’ greenhouse gas inventories. Local accounts can then be nested within national inventories without double counting.

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Australian local governments can do many things to help reduce their community emissions.
Australian Local Government Climate Review 2018, CC BY

By measuring greenhouse gas emissions at the local scale, the protocol supports local governments and communities as important actors in climate governance. Adding local efforts together gives them a stronger voice in national and international arenas. This political pressure is especially important given the inadequacy of countries’ commitments to meet the Paris Agreement targets.

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Translating local actions to global impacts

Even though the protocol adds weight to local climate commitments, translating these commitments into action can be challenging. Consistent with IPCC standards, the protocol frames greenhouse gases in two important ways.

First, greenhouse gases are measured according to defined “sectors”. These include stationary energy, transportation, waste, industrial processes and product use, and agriculture, forestry and other land uses. These categories are shorthand for the complex and extended systems of infrastructure, resource flows and human activities that produce greenhouse gases.

Municipal boundaries often align poorly with these systems. The data on activity needed to calculate emissions are often patchy or misaligned at the local scale. Local governments and communities rarely have the authority to intervene directly and change these larger systems.

So although the protocol helps to direct attention to local activities and systems that produce emissions, changing those systems and activities is usually more complex.

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This is why we cannot rely on cities alone to tackle climate change

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Second, greenhouse gas emissions are translated, through a set of simple equations established by the IPCC, into a “carbon dioxide equivalent”. These equations are the basis for comparing, aggregating and exchanging greenhouse gas emissions and removals of different types, at different times and in different places.

These calculations are entangled with the claim that “a ton of carbon is everywhere the same”. It forms the basis for regulated and voluntary markets in carbon trading.

However, there are problems with this assumed interchangeability. As Larry Lohmann argues:

While carbon trading encourages ingenuity in inventing measurable ‘equivalences’ between emissions of different types in different places, it does not select for innovations that can initiate or sustain a historical trajectory away from fossil fuels […]

Local carbon accounts aren’t the whole answer

In sum, the Greenhouse Gas Protocol supports the legitimacy and strengthens the voice of local governments and communities in global climate governance.

At the same time, defining emissions by territory and sector does not fully reflect the complexity of the infrastructure systems and human activities that cause emissions. In particular, the protocol can reinforce a framing of carbon as an exchangeable commodity. This poses the risk that choices about whether to reduce or offset emissions could be skewed.

Without suggesting there is no place for territorial carbon accounts, it is important to recognise that how we measure emissions shapes possibilities for how we might manage them.

Alternative approaches such as consumption-based accounts measure greenhouse gas emissions from what is consumed by an individual or within a territory. This draws attention to choices about what we eat and what we buy, and to the social norms and systems of wealth, which are harder to see in territorial accounts.

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The key point is that no single measure of greenhouse gases can offer a definitive view. As a complement to the protocol, an additional question for local governments and communities to ask when trying to manage greenhouse gases is: “Where do we have the power to effect change, and why does that change matter to us?”

Stephen Pollard, PhD Candidate in climate change and sustainability, University of Melbourne

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