Thousands of alien species could invade the Arctic

Warmer temperatures and more tourists make it easier for non-native species to get a foothold in northern outposts.

Norwegian University of Science and Technology

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In recent years, a surprisingly large number of alien species have managed to flourish in Svalbard. In 2024, common meadow rue, Thalictrum flavum ,was identified for the first time in Svalbard, in full bloom on a nutrient-rich slope in Barentsburg. 

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Credit: Photo: Kristine Bakke Westergaard, NTNU University Museum

Species that are not native to an area can displace species that already live there. The Intergovernmental Panel on Nature (IPBES) considers this to be one of the greatest threats to species diversity on our planet.

Researchers have now catalogued which alien plants may pose a threat to plants in the Arctic. The results are concerning, particularly at a time when it has probably never been easier for alien species to spread.

"We found a total of 2554 species that would find a suitable climatic niche in today's Arctic," says Kristine Bakke Westergaard, an associate professor at the Department of Natural History at the NTNU University Museum (at the Norwegian University of Science and Technology, NTNU).

This means that these plants have a chance of making it in the Arctic if they manage to find a way there. One of the most probable transport mechanisms is hitchhiking on, or with, humans.

"Our results show that alien species from virtually all over the world can find a niche in the Arctic. And with all the human activity in the Arctic now, there are lots of opportunities to get there,” Westergaard said.

Data from more than 51 million occurrences

She and colleagues from the Department of Natural History and the University of Liverpool have conducted what is called a "horizon scan".

"We looked at roughly 14,000 known alien plant species that can spread to places where they do not originally belong," Westergaard said.

The researchers used data from over 51 million known occurrences of these species. They found this information in the GBIF—the Global Biodiversity Information Facility, in large databases and in the scientific literature.

First author Tor Henrik Ulsted was a master's student at the NTNU University Museum until 2024. Ulsted won the Faculty of Natural Science's award for best the master's thesis that contributes to sustainable development, and has since worked to publish this article.

Norway a high-risk country

The researchers used the data to create a map that provides an overview of the most threatened areas.

"Our map shows hotspot areas in the Arctic where many alien species can tolerate the climate. The highest number of species are found in the north of Norway," Ulsted said.

While Norway is among the high-risk areas, few, if any, places in the Arctic are completely safe, including Svalbard.

"Even in Svalbard,  86 alien species can find a climatic niche," says Westergaard, who has found and studied alien species there herself.

Conditions in the north are changing rapidly. In recent years, it has generally become warmer in the Arctic, meaning that more and more alien species can find a possible niche where they can thrive.

Tools for those assessing the threat

The Norwegian Biodiversity Information Centre's expert committees for Norway and Svalbard assess the risk of alien species in different areas.

"These committees have long found it to be very laborious, almost impossible, to make a list of relevant species that should be assessed as possible new alien species," says Westergaard.

The new methodology will help experts in these committees to look at the species lists  and assess the ecological risk for each of the species in the relevant areas.

"Our long-term goal is to help identify alien species before they become invasive and problematic," Ulsted said.

It is much more effective to identify and manage invasive species as early as possible rather than waiting until they are well established.

Westergaard says this approach also supports the goals of the Kunming-Montreal Global Biodiversity  Framework, among which is reducing the threat from alien species, including by halving the introduction and establishment of alien species by 2030.

It is also in line with several of the measures in the Norwegian authorities' action plan against alien organisms. (Combating harmful alien organisms – Action plan 2020–2025 in Norwegian)

Reference:
Ulsted TH, Westergaard KB, Dawson W, Speed JDM (2025) Horizon scanning of potential new alien vascular plant species and their climatic niche space across the Arctic. NeoBiota 104: 1-26. https://doi.org/10.3897/neobiota.104.165054

  

This map shows hotspots for possible new alien vascular plants in the Arctic. The lighter the colour, the higher the number of potential species per 1 x 1 km.

Credit

Illustration: NTNU University Museum

The slope below the old barn and farm buildings in Longyearbyen is very nutrient-rich  after manure and food scraps were dumped there for years. It’s a great place where new alien species can get established. 

Human activity brings with it alien species and creates excellent conditions that allow them to become established in an otherwise barren Arctic landscape. The slope below the old barn and farm buildings in Barentsburg is very nutrient-rich after manure and food scraps were dumped there for years. New alien species appear here at regular intervals, even though farming ceased many years ago. 

Credit

Photo: Kristine Bakke Westergaard, NTNU University Museum

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Journal

NeoBiota

DOI

10.3897/neobiota.104.165054 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Horizon scanning of potential new alien vascular plant species and their climatic niche space across the Arctic

 

Fish face smaller meals due to warmer seas and fishing

University of Essex

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Fish across Britain’s seas face ever-smaller meals as warmer seas and commercial fishing squeeze ocean food webs, new research suggests.

Research by the University of Essex and the UK Government’s Centre for Environment, Fisheries, and Aquaculture Science (Cefas) found strain across warm and highly fished areas of the Northeast Atlantic leaving predators such as cod, haddock and thorny skate, with less energy from every meal.

The researchers examined data from the stomach contents of more than 50,000 marine predators collected over 35 years from waters including the North Sea, English Channel and Norwegian Sea.

They found that in warmer waters, predators were feeding on smaller fish and invertebrates such as sprat, krill and crabs.

That matters because smaller meals deliver less energy, potentially weakening predators and making marine ecosystems more fragile.

The problem is intensified in areas of high commercial fishing, where larger species are typically more heavily depleted.

This reduces the average size of prey available, compounding the effects of climate change such as increases in sea surface temperatures.

Lead researcher Amy Shurety from the School of Life Sciences said the study shows that the impacts of climate change and commercial fishing need to be looked at together to protect ocean ecosystems.

She said: “Sustainable fishing and eating a more diverse range of seafood at home, can help protect marine ecosystems as the climate changes.”

The study, published in Nature, shows prey species are shrinking not because large species are disappearing, but because individual animals within the same species are getting smaller.

This is because warmer water speeds up metabolism, holds less oxygen and favours smaller bodies that are easier to sustain.

As prey shrink, predators respond by targeting a wider range of species and seeking out the largest prey still available.

Each 1°C rise in temperature leads to about a 1.8% decrease in the size of prey predators eat.

But feeding on more prey lower down the food chain can make energy transfer less efficient, leaving top predators potentially with less fuel to survive and reproduce.

The researchers warn this could undermine the long-term resilience of marine ecosystems unless fisheries policy shifts towards managing entire food webs, rather than individual species in isolation.

Ms Shurety added: “Marine ecosystems are often hit by multiple pressures at the same time and looking at these pressures one by one can hide what’s really happening.

“Our findings show that in oceans that are both warmer and heavily fished, predators must eat more smaller prey to survive.

“This combined effect would be missed if dynamics of climate change and commercial fishing were considered separately.

“Which suggests that to protect marine food webs, it’s essential that climate change and fisheries are managed together, not in isolation.”

The researchers used the diet data collated by Cefas.

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Journal

Nature Communications

DOI

10.1038/s41467-025-67362-8 

Method of Research

Data/statistical analysis

Subject of Research

Animals

Article Title

Commercial fishing amplifies impacts of increasing temperature on predator-prey interactions in marine ecosystems

 

Shrinking shellfish? FAU study uncovers acidic water risks in Indian River lagoon

Florida Atlantic University

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FAU researchers measured aragonite saturation – a key indicator of water’s ability to support calcifying organisms like oysters and clams – throughout the Indian River Lagoon.

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Credit: FAU Harbor Branch

Florida’s Indian River Lagoon (IRL), one of the state’s most ecologically productive estuaries, is facing a growing but invisible threat that could reshape its marine ecosystems. Over the past decade, the lagoon has suffered severe degradation caused by nutrient pollution, excessive freshwater runoff, harmful algal blooms (HABs), and declining water quality. These changes have led to the loss of tens of thousands of acres of seagrass and have negatively impacted shellfish, fish, dolphins, manatees and other key species.

A new study from Florida Atlantic University’s Harbor Branch Oceanographic Institute now reveals that these pressures are also contributing to coastal acidification, a chemical shift in the water that threatens the ability of shell-building marine organisms to grow and thrive. 

Many marine animals, including oysters and clams, rely on a mineral called aragonite to build shells and skeletons. Scientists measure the water’s ability to support aragonite using aragonite saturation (Ωarag).

To understand these changes, FAU Harbor Branch researchers studied the IRL from 2016 to 2017, measuring Ωarag and other water chemistry factors. They examined how nutrients, freshwater inputs, and other environmental conditions affect the lagoon’s ability to support shell-building marine life.

The study used two approaches. First, researchers conducted a broad survey across the lagoon, from nutrient-rich northern areas to southern regions affected by freshwater inflows. Second, they did weekly sampling at three central sites with different salinity and land-use conditions: an urban-influenced canal, a river mouth affected by urban and agricultural runoff, and a relatively natural reference site with strong ocean exchange.

Results of the study, published in the journal Marine Pollution Bulletin, revealed clear patterns. Northern sites with high nutrient concentrations and frequent HABs had lower aragonite saturation. Southern sites, influenced by freshwater discharges, also had lower Ωarag, primarily due to reduced salinity and dilution of aragonite. In the weekly surveys, Ωarag was positively correlated with salinity and negatively correlated with nutrient levels, confirming that both freshwater input and nutrient pollution play a role in controlling water chemistry.

“For shell-building organisms, the consequences are clear,” said Rachel Brewton, Ph.D., co-author and an assistant research professor, FAU Harbor Branch. “When aragonite saturation drops, growth slows and shells become weaker, leaving animals more vulnerable to predators, disease and stress. Over time, this can disrupt the food web, affecting fish, dolphins, and the human communities that rely on these species. Shrinking shellfish are more than a curiosity – they’re a warning for the entire ecosystem.”

This research provides the first comprehensive documentation of aragonite saturation throughout the entire IRL, filling a critical gap in our understanding of coastal acidification in shallow estuaries. Prior studies focused on nutrient pollution, algal blooms, or freshwater inflows, but none had examined how these factors interact to impact the water’s chemistry and the health of shell-building organisms.

“Coastal acidification occurs when carbon dioxide, CO₂, from the atmosphere or from biological processes, such as microbial activity associated with decaying algae, dissolves in seawater. This CO₂ reacts with water to form carbonic acid, which lowers the water’s pH and reduces the amount of carbonate ions available for shell-building,” said Brian Lapointe, Ph.D., senior author and a research professor, FAU Harbor Branch. “In addition to atmospheric CO₂, nutrient pollution from urban runoff, agricultural sources, and wastewater can fuel algae growth. When these algae die and decompose, the process produces more CO₂, further acidifying the water.”

Other factors, such as freshwater inflows from rivers and canals, also influence aragonite saturation by diluting the water and lowering salinity and mineral concentrations. In shallow estuaries like the IRL, where water circulation is slower than in the open ocean, these effects are amplified, creating localized hotspots where shell-building organisms are especially at risk.

The results have broader implications. Estuaries worldwide are experiencing similar pressures from population growth, land-use changes, stormwater runoff, and nutrient pollution.

“By identifying the environmental conditions that lower aragonite saturation, we can start to develop strategies to mitigate coastal acidification,” said Megan Conkling, Ph.D., first author and research scientist at FAU Harbor Branch. “Managing nutrient inputs and freshwater flows more carefully could help protect oysters, clams, seagrass, and other critical species. Our work provides a roadmap for designing restoration and mitigation efforts, not just in Florida, but in estuaries around the world.”

The study also emphasizes the importance of ongoing monitoring. FAU Harbor Branch’s Indian River Lagoon Observatory Network of Environmental Sensors (IRLON) has been upgraded to track pH and CO₂ levels, which allows scientists to calculate aragonite saturation in near real-time. This IRLON data can help forecast future changes, identify vulnerable species and habitats, and guide targeted management actions.

“Protecting the Indian River Lagoon requires understanding not just what we can see on the surface, like algae blooms or seagrass loss, but also the invisible chemical changes affecting marine life,” said Conkling. “This study provides essential insight into one of the less visible but critical threats facing estuaries today.”

Study co-authors are Bret R. Kaiser; and Kristen S. Davis, IRLON manager, both with FAU Harbor Branch; and Mingshun Jiang, Ph.D., associate research professor, FAU Harbor Branch.

This research was supported by the Harbor Branch Oceanographic Institute Foundation through the Saves Our Seas Specialty License Plate Program awarded to Lapointe.

- FAU -

About Harbor Branch Oceanographic Institute:
Founded in 1971, Harbor Branch Oceanographic Institute at Florida Atlantic University is a research community of marine scientists, engineers, educators, and other professionals focused on Ocean Science for a Better World. The institute drives innovation in ocean engineering, at-sea operations, drug discovery and biotechnology from the oceans, coastal ecology and conservation, marine mammal research and conservation, aquaculture, ocean observing systems and marine education. For more information, visit www.fau.edu/hboi.

 

About Florida Atlantic University:

Florida Atlantic University serves more than 32,000 undergraduate and graduate students across six campuses along Florida’s Southeast coast. Recognized as one of only 11 institutions nationwide to achieve three Carnegie Foundation designations - R1: Very High Research Spending and Doctorate Production,” “Opportunity College and University,” and Carnegie Community Engagement Classification - FAU stands at the intersection of academic excellence and social mobility. Ranked among the Top 100 Public Universities by U.S. News & World Report, FAU is also nationally recognized as a Top 25 Best-In-Class College and cited by Washington Monthly as “one of the country’s most effective engines of upward mobility.” To learn more, visit www.fau.edu.

  

FAU researchers measured aragonite saturation – a key indicator of water’s ability to support calcifying organisms like oysters and clams – throughout the Indian River Lagoon.

Credit

FAU Harbor Branch

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Journal

Marine Pollution Bulletin

DOI

10.1016/j.marpolbul.2025.119175 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Coastal eutrophication and freshwater inputs drive acidification in the Indian River Lagoon, Florida