A dedicated team of historical ecologists from the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences recently concluded their fieldwork on the remote Commander Islands, an archipelago deeply woven into the fabric of global environmental history. As they meticulously process the collected scientific data, their ongoing mission is to unravel the mysteries of past ecosystems, particularly those of recently extinct species. Their groundbreaking work aims to shed light on critical questions surrounding the Steller’s Sea Cow and Steller’s Cormorant: where they truly lived, the true causes of their disappearance, and what these historical events can teach us about environmental change today.
Often mistakenly referred to as paleoecologists, this scientific discipline, historical ecology, offers a nuanced perspective on environmental change. Unlike paleoecology, which typically delves into epochs hundreds of thousands or millions of years ago, historical ecologists focus on the dynamic evolution of modern ecosystems over the last 10,000 to 12,000 years — the Holocene epoch. Arkady Savinetsky, head of the Historical Ecology Laboratory at the A.N. Severtsov Institute, recounts his own journey into this field, shifting from traditional ornithology to seeking the underlying causes of ecological phenomena, an intellectual curiosity ignited by the unexpected nesting habits of steppe eagles in newly planted groves. This shift highlighted a fundamental principle: species ecologies are not static, and current assumptions about their habitats can be misleading.
This ‘actualistic method’ is central to their research. It involves understanding current ecological processes to interpret past ones. For instance, while we might associate lemmings solely with tundras or jerboas with steppes, historical data reveals a more fluid reality. Northern reindeer, once thought to be purely arctic, historically inhabited extensive forest zones extending into Mongolia and parts of European Russia. Similarly, the water vole, now strongly associated with aquatic environments, was historically a ‘plakorny’ species, thriving on uplands. These examples underscore how adaptive species truly are and how human perception can lag behind scientific understanding of ecological shifts.
One of the prime subjects of their inquiry is Steller’s Sea Cow (Hydrodamalis gigas), a colossal marine mammal discovered in 1741 and driven to extinction within decades. Recent genomic sequencing, spearheaded by scientists like Fyodor Sharko and Artyom Nedoluzhko, suggests that while human hunting undeniably accelerated its demise, the species was already on a trajectory toward extinction due to natural factors, such as the ‘Little Ice Age’ and associated ice formation that would have inflicted injuries. A significant enigma remains its true geographical distribution. While isolated remains are found on Aleutian Islands, it is unclear if these represent resident populations or carcasses carried by currents. Archaeological digs on islands like Adak, revealing 6,800-year-old human settlements, have yielded no sea cow bones, deepening the mystery of its presence on the remote Commander Islands.
Equally compelling is the case of Steller’s Cormorant (Phalacrocorax perspicillatus). Skeletal remains have been found on the Commander Islands and, surprisingly, in Japan, separated by a vast 120,000-year time span. Yet, the Kuril Islands, strategically located between these two points and extensively studied, have yielded no trace of the bird. Discovered in 1741, it is believed to have vanished by 1852. Debunking a long-held myth, morphological analysis of fossil bones has definitively shown that Steller’s Cormorant was not flightless, as once speculated, but a perfectly capable, albeit large and heavy, flyer. Genetic analysis of this species is now underway, promising further revelations.
To unlock these biological secrets, the team employs sophisticated scientific methodologies. Radiocarbon dating, a cornerstone technique, allows scientists to determine the age of organic remains by measuring the decay of Carbon-14 isotopes absorbed during an organism’s life. However, dating marine organisms presents a unique challenge known as the ‘reservoir effect.’ Due to the complex circulation of carbon in oceans, a modern marine animal might appear to be 400 years old through standard radiocarbon dating. This effect varies geographically, with the North Pacific showing a 525-year discrepancy, and the Commander Islands exhibiting an even more pronounced 700-year difference, necessitating careful calibration.
Another powerful tool is stable isotope analysis. Stanislav Samsonov, a key member of the historical ecology team, explains that this method doesn’t literally tell you what an animal ate, but it reveals its trophic level – the position it occupies in a food web – and the general location of its feeding grounds, whether coastal, pelagic, or terrestrial. By analyzing Steller’s Cormorant bones, they have determined that its diet and trophic level were similar to those of its contemporary relatives, the Bering’s and Red-faced cormorants, suggesting a diet of small fish and crustaceans in coastal waters. Initial findings even suggest a distinct ecological niche for larger cormorant species, which they continue to explore.
Physical characteristics are also deciphered from skeletal remains. The estimated weight of Steller’s Cormorant, approximately 3,800 grams (compared to 1,100-2,100g for Bering’s and 1,800-2,700g for Red-faced cormorants), confirmed it as the largest cormorant species before its extinction. Its bone morphology also indicates its hunting style: unlike other diving birds, cormorants use their feet, not wings, for propulsion underwater. Steller’s Cormorant, with its specialized leg structure, was adept at hunting near the seafloor in coastal areas, prioritizing precision over chasing fast-moving schools of fish.
The recent discovery of remarkably well-preserved Steller’s Cormorant skeletons on the Commander Islands, unearthed from previously buried sand layers, has been a monumental breakthrough, providing material for these detailed analyses. These finds are globally significant, given the species’ rarity in museum collections. As with the sea cow, while human activity likely played a role in its rapid disappearance, mass epizootics (animal epidemics) are also considered a potential contributing factor, preventing its recovery unlike other resilient species.
Arkady Savinetsky emphasizes that historical ecology extends beyond mere academic curiosity; it is a vital lens through which to understand our present and future. While popular understanding often equates ‘ecology’ with pollution and conservation, the scientific definition encompasses the study of interconnected global systems. By constructing hypothetical models based on past ecological events – be it species extinctions or climate shifts – historical ecologists can offer critical insights into potential future scenarios. The Earth has experienced numerous warming and cooling periods, including ice ages when vast ice sheets were absent. From a natural perspective, climate shifts are cyclical; from a human perspective, they represent existential challenges. Understanding past environmental resilience and vulnerabilities is crucial for navigating modern anthropogenic changes.
Savinetsky’s personal connection to the Commander Islands dates back to 1991, following archaeological work in Chukotka. The islands, he explains, are a unique natural laboratory: out of only two species that went extinct in the North Pacific in the last 500 years, both are found here. Early analysis of sea cow bones from the islands helped disprove the ‘last slaughter’ hypothesis, revealing a long history of declining populations. His extensive work across the Aleutian Islands since 1994 further enriched the understanding of regional ecosystems, only paused by the recent global pandemic.
The fragility of island ecosystems, with their limited area, often makes them highly susceptible to climatic and anthropogenic pressures, as demonstrated by the Commander Islands. A lingering question remains regarding the apparent absence of these extinct species on the continuous Aleutian chain. Furthermore, the lack of definitive evidence of human presence on the Commander Islands prior to Bering’s arrival, despite thousands of years of human migration through the Aleutians, presents another archaeological enigma. Tectonic activity in the region, which can raise or submerge ancient settlement sites, complicates this search. Despite these challenges, the team continues its work, funded by a Russian Science Foundation grant, driven by the profound scientific interest these isolated outposts hold.
The current phase of research involves extensive analysis of gathered bone samples and cutting-edge environmental DNA (eDNA) analysis of peat bog samples from the Gavan River valley, a former marine lagoon. These samples, some overlaying 7,000-year-old volcanic ash from a powerful Kamchatka eruption, promise to yield invaluable information on ancient animal populations, past climates, and vegetation. With two years remaining in their current grant cycle, Savinetsky, Samsonov, and their colleague Oleg Petrov are piecing together a comprehensive ecological tapestry of the Commander Islands, hoping to reveal not just where extinct species lived, but how their lives, and deaths, resonate with the ecological challenges of our contemporary world.