© iStock / Koldunov

Snapshot of an ever-changing Arctic: The state of Arctic terrestrial biodiversity

Climate change is driving significant changes that could lead to ecological catastrophes in the Arctic

The Arctic is home to thousands of unique species that have adapted to survive cold environments and highly variable climatic conditions. As hardy as they can be, Arctic terrestrial ecosystems are under pressure. Terrestrial ecosystems are impacted by industrial development and climate-driven thawing permafrost, extreme weather events, changes in precipitation and snow cover, fires, invasive species and more.

Exactly how these pressures affect terrestrial species and ecosystems is difficult to determine because the Arctic’s complexity and size make it challenging to detect and attribute changes. The Conservation of Arctic Flora and Fauna (CAFF)’s Circumpolar Biodiversity Monitoring Program (CBMP) monitors and reports on key biotic components in the Arctic environment to help detect circumpolar changes and provide advice for decision-making.

Recently, the CBMP released the first State of the Arctic Terrestrial Biodiversity report (START), which summarizes the status and trends of key elements of the Arctic terrestrial environment, and provides advice to improve biodiversity monitoring. Over 180 experts from across the Arctic were involved with compiling the report.

“CAFF’s CBMP developed a monitoring plan for terrestrial biodiversity over seven years ago,” says Tom Christensen, Co-Chair of CBMP. “This report is a milestone because it’s the first time we looked at the monitoring methods that different Arctic States have used and put them together in one agreed-upon report.”

Climate change-driven lifecycle mismatches are a leading stressor for wildlife

Arctic terrestrial biodiversity is undergoing rapid change, with climate change being the overwhelming driver, according to the report. One consequence of these changes is a phenological mismatch between species’ life cycles.

“We’re seeing more of a mismatch between flora, pollinators and birds,” says Mora Aronsson, Co-Chair of CBMP Terrestrial. “For example, as the climate warms and seasons change, ecological cues are thrown off. Plants flower earlier, and some insects are slower to respond to that. Arctic migratory birds for the most part are in another part of the world when this starts happening, and they may arrive to see their food sources impacted. Looking to the future, this mismatch is one of the greatest threats to Arctic wildlife. It could lead to ecological catastrophes.”

Impacts to Arctic terrestrial species will be felt globally. “Changes in Arctic biodiversity have an influence on species that are seen in more southern locations,” says Tom Christensen. “If migratory birds can’t get food when they’re breeding in the Arctic, that’ll have a major impact on the overall global population of these species and the ecosystems that they spend time in when outside of the Arctic.”

New residents from the South

A warmer and longer growing season may be an advantage for some species, but specialized Arctic wildlife could be negatively affected. For example, vegetation productivity has increased significantly across the entire Arctic, in part because of increased growth and encroachment of shrubs and trees. At the same time, there’s also been reduced cover of more typical Arctic species such as lichen and moss. Southern species moving into the Arctic reduce space for northern species and complicate their interactions.

The START reports that range extensions of more southern species such as red fox, moose, American beaver and snowshoe hare, are introducing new herbivore competitors and potential predators into Arctic ecosystems.

“Arctic biodiversity is unique because it’s condensed in a small area,” says Tom Christensen. “We can see that because of climate change, and as southern species move North, Arctic species will have to move even further North. Eventually, there won’t be any space for them left.”

So far, the impacts of southern invasive species on Arctic species are unclear. But it may not be long before it becomes a more prominent issue in the Arctic. “Invasive species establishing themselves in the Arctic may be starting off very slowly, but as the invasive species accumulate, they can grow exponentially as time goes on,” says Starri Heiðmarsson, Co-Chair of CBMP Terrestrial.

“Luckily, we’ve been able to monitor this issue of invasive species, and it’s early enough that there are things we can do to prevent problems. For example, there’s an eradication program for invasive plants in Svalbard, when just five or ten years ago there had been no reason for such a program,” adds Mora Aronsson.

Diverse, unpredictable changes in terrestrial Arctic ecosystems are expected to worsen

The START finds that climate change affects species differently with no consistent pattern. For example, global populations of reindeer have mostly declined since the 1990s, some dramatically, but with notable exceptions. In years of late snowmelt, ground-nesting shorebirds experience breeding failure. Heavy rain events and warm spells that lead to large blackfly outbreaks reduce breeding success in peregrine falcons.

These changes impact culturally important food resources, affecting the food security and cultures of Arctic Indigenous peoples and residents. For example, Indigenous knowledge indicates increasing changes in year-to-year berry abundance. In recent years, unprecedented outbreaks of defoliating insects have caused severe declines in berry yields for Indigenous peoples, which are an important nutrition and vitamin source for local communities. Reindeer declines can also have a significant impact on food security and ways of life.

“Something to keep in mind is that much of the changes that have happened – and extreme events and tipping points – aren’t linear or even logarithmic,” says Mora Aronsson. “What we can see is a catastrophic way of change – suddenly something unexpected.”

That’s why establishing and supporting long-term monitoring to gather circumpolar knowledge is critical to understand the changes already underway in the Arctic. Changes in Arctic terrestrial environments are fundamentally diverse and can depend on geographic location. The START points out that summarizing these changes at the circumpolar scale may hide more dramatic changes at the local level. However, harmonizing data collection across geographies will allow for cohesive monitoring at the local and circumpolar scale.

“Climate change is the great driver of these changes we are witnessing, and it’ll probably be more evident and severe as time goes on,” says Starri Heiðmarsson.

“In that sense, the START report is important in comparing what we know now, but it’s not less important in trying to synchronize and harmonize how we’re observing these changes and how we can compare them in the future. We need to be speaking the same language when it comes to monitoring methods to make things more easily comparable in different geographies.”

“We hope that these key findings will help inform the decision makers on some of the changes that are happening,” says Tom Christensen. “We have a lot of data in the report that show the status of terrestrial biodiversity from the different Arctic States. At the same time, the report comes out with knowledge gaps and advice on needs and next steps for monitoring. We hope decision makers in the Arctic States see the importance of working together on this in the future.”

“We stress that while there are still knowledge gaps, we have a lot of information in the report – certainly enough to start doing something about it,” adds Mora Aronsson. “You can start with the START report to take action to conserve terrestrial biodiversity.”