Lake Baikal, nestled in southern Siberia, stands as the oldest and deepest freshwater lake in the world. Its unique combination of age and isolation has fostered an exceptional level of biodiversity. However, this extraordinary ecosystem faces threats from global warming. Jeffrey McKinnon, in his work “Our Ancient Lakes: A Natural History” (MIT Press, 2023), delves into the significant changes currently unfolding in this lake.
Lake Baikal, the planet’s most voluminous freshwater lake, holds 20% of Earth’s unfrozen fresh water. Given its size and depth, one might assume it to be resilient to environmental changes. Yet, research initiated in the 2000s, based on 60 years of data collected by Mikhail Kozhov, Olga Kozhova, and Lyubov Izmest’eva, has sparked significant interest.
This research has conclusively shown that Lake Baikal is warming, leading to a reduction in the duration of its ice cover. These climatic changes are impacting the lake’s biological community, both directly and indirectly, by altering physical processes within the lake and the interactions among its organisms.
In a landmark study, Stephanie Hampton, alongside Izmest’eva and a team from various institutions, presented the first comprehensive analysis of these changes. They observed an increase in algal mass and a rise in the population of cladocerans, a type of zooplankton that thrives in warmer temperatures. Conversely, the population of the cold-loving crustacean Epischurella has seen a slight decline or remained stable. These shifts in zooplankton populations could significantly impact nutrient cycling within the lake, leading to wide-ranging ecological effects.
Further analysis by George Swann and Anson Mackay, using data from shallow sediment cores, has shed light on how both natural and human-driven changes have influenced nutrient and chemical cycling in the lake. Their findings suggest a significant increase in nutrient supply since the mid-19th century, primarily due to stronger winds over the lake, which in turn is likely a result of decreased ice cover and warmer temperatures.
Lake Baikal is home to the unique freshwater seal species, the nerpa (Pusa sibirica), highlighting the lake’s rich biodiversity. Hampton and Izmest’eva have expanded on these findings through a mathematical model of the Baikal open water ecosystem. This model aims to integrate the biological interactions among organisms with changes in the physical environment, offering insights into the causes of recent shifts in seasonal algae abundance.
Traditionally, Lake Baikal experienced peaks in algae productivity during the clear ice of winter and early spring. However, these peaks have been delayed, weakened, or absent in recent decades. The model suggests that reduced ice cover may be a primary factor behind these changes, with potential implications for the lake’s winter algae peak.
The concept of a “regime shift” described in the model highlights the possibility of abrupt and potentially irreversible changes in ecosystems due to global warming and other human-induced environmental changes. Lake Baikal’s history, dating back to the time of the dinosaurs, and its diverse endemic fauna, including gammarid amphipods and sculpins, underscore the lake’s ecological significance.
As the most biodiverse ancient lake at the highest latitude, Baikal’s response to global warming offers a cautionary tale about the broader impacts of climate change on ecosystems. This lake’s experience serves as a reminder of the urgent need to address global warming, not only for the sake of Lake Baikal but for the health of our planet as a whole.