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Healthy Ecosystems

Biodiversity and Ecosystem Function

The Lake Champlain Basin’s species and habitat diversity is rich, though some habitats are fragmented and need protection.

Native species rely on intact and functioning habitats such as forests, floodplains, and wetlands. These habitats also provide other invaluable ecosystem functions, including nutrient cycling, sediment retention, carbon storage, and air and water purification. Vegetated lake shorelines and riparian (river) buffers help mitigate flood impacts by absorbing water, reducing erosion, and providing shade and refuge that help keep these waterbodies cool and habitable for fish, amphibians, and insects.

Fragmented habitat and the pressures of climate change can put rare, threatened, and endangered species at risk. Habitat fragmentation mostly comes from human development and land use and can limit species’ ability to reproduce, thrive, and move under natural conditions. Native species’ habitat becomes stressed even further when intense rainfall creates disturbed areas that favor non-native and invasive species.  

About 40% of the Basin’s land area is conserved to some degree; this protects these lands from future exploitation such as surface mining, waste dumping, and development. Conservation efforts can increase the biodiversity, resilience, and functioning of ecosystems and expand opportunities for human use and enjoyment of the Basin.  

More research is needed to support the Basin’s rare, threatened, and endangered species.

Fish and wildlife biologists are working hard to better understand and protect the Basin’s rare, threatened, and endangered species such as the spiny softshell turtle, lake sturgeon, Indiana bat, common tern, and mudpuppy.

While some species like the bald eagle and the common loon are making great recoveries as a result of habitat protection, pollution reduction, and reintroduction methods, more research is needed for the recovery of other species. The Vermont Fish and Wildlife Department is relocating mudpuppies to an upper reach of the Lamoille River and tracking their movement to determine if a viable population may be established in more protected habitat. Five of the ten known native mussel species in Lake Champlain are listed as threatened or endangered in Vermont. The Lake Champlain Committee studied the impacts of invasive zebra mussels on native mussel species and identified the Lamoille River delta as suitable refugia habitat from zebra mussels. Protection of these areas will help endangered species thrive in the future.

Landlocked Atlantic salmon have more access to historic river habitat, and passage for all aquatic species is being addressed through culvert replacements.

When connected and well buffered, Lake Champlain’s river systems are home to many native species. They absorb flood waters, retain sediment, and provide cool water habitat for species like trout and salmon. However, this network has been disrupted by dams, development, agriculture, industry, and road crossings. Stream culverts at road crossings are often undersized or damaged. These culverts can be plugged with sediment and debris or are “perched” from the streambed; thus, they make passage difficult for fish and other species. 

landlocked Atlantic salmon
The recent removal of dams has increased habitat for landlocked Atlantic salmon. Photo: Concordia University

Fisheries biologists are working to restore fish passage in Lake Champlain’s tributaries, especially for landlocked Atlantic salmon (Figure 11). Salmon have upstream access to most of their historic range in most major tributaries, except the Saranac and Missisquoi Rivers. More work is needed in these systems to restore salmon access to spawning grounds. In the Winooski River, intensive restoration efforts have focused on the use of fish ladders and trapping and trucking salmon upstream, thus extending the historic range of this species. In the Ausable River, biologists are using environmental DNA to map native and non-native fish distributions, including brook trout, brown trout, and rainbow trout to prioritize future connection and Atlantic salmon habitat restoration efforts. Other groups, including Dam Task Forces in New York and Vermont, identify, prioritize, and implement river passage restorations.

Figure: Landlocked Atlantic salmon habitat access in Lake Champlain tributaries
Figure 11 | Landlocked Atlantic salmon habitat access in Lake Champlain tributaries

Lake Champlain’s fish are enjoyed by anglers, and more research is needed to determine the status of the Lake’s fish populations.

Lake Champlain is home to 80 species of fish, including sport fish that attract fishing tournaments of all sizes. Lake Champlain has great angling opportunities year-round. The largest lake trout on record was caught in August 2020; it weighed 19 lbs., 6 oz., and measured over 36″ long.

Restoration projects for certain fish species are underway, but the status of many other species in Lake Champlain is unknown. The University of Vermont is leading a fish community monitoring study to determine the best approach to collecting information on the abundance and condition of forage fish such as alewife and rainbow smelt. Changes in the availability of forage fish will affect predator species, like trout and salmon, in the Lake.

Lake trout stocking will be reduced due to successful natural reproduction, and stocking of other salmonid fish will continue.

Lake trout, Atlantic salmon, brown trout, and rainbow trout/steelhead continue to be stocked in Lake Champlain to support the Lake Champlain angling fishery. The University of Vermont biologists have found nine age classes of wild (not stocked) lake trout. Lake trout were gone from Lake Champlain by 1900, and this discovery has led to the first-ever planned reduction in lake trout stocking by 33% in 2022 to maintain a healthy balance between wild and stocked lake trout and their forage fish base. Fishery managers continue to monitor adult landlocked Atlantic salmon and collect eggs from wild fish for hatchery production. The majority of salmon collected from 2018–2020 have been from Hatchery Brook and the Lamoille River in Vermont and Boquet River and Saranac River in New York. Each fall, three- and four-year-old salmon undergo a spawning migration from the Lake to rivers to reproduce. These river-run salmon provide fishing opportunities and are critical to ongoing efforts to restore natural populations.

Climate change and invasive forest pests are putting pressure on the Basin’s forested habitats.

Climate change may be the greatest threat to the Basin’s forest health. Northern hardwood species such as maple, yellow birch, and American beech are threatened by warmer and drier growing seasons that can stunt growth and shift forest compositions toward warmer-climate species like oak and pine.

Two invasive forest pests, the emerald ash borer and hemlock woolly adelgid, have recently been detected in the Basin. These pests have spread with assistance from humans as they hitchhike in firewood and infested nursery stock and then naturally disperse. Ash and hemlock trees are important species in the Basin’s natural landscape, and these pests’ impacts can kill host trees quickly, causing erosion and water quality impacts from the steep slopes and riparian areas they occupy. Forest managers are conducting routine monitoring and rapid-response containment of hemlock woolly adelgid infestations in the Lake George watershed, where hemlocks make up 80% of the forested watershed.

Air temperatures are rising, and the Lake freezes over less often than in the past, though the full impacts of climate change on habitats, fish, and wildlife are difficult to quantify.

Figure: Seasonal air temperature trends in Burlington, Vermont
Figure 12 | Seasonal air temperature trends in Burlington, Vermont

Air temperature measurements indicate that winter minimum and summer maximum air temperatures have increased since the early 1900s, with pronounced warming in recent decades (Figure 12). Burlington experienced its hottest summer on record in 2020, with an average temperature of 72.3°F and a record 41 consecutive days above 60°F, breaking a previously held record in 1898 of 37 days. These trends may affect ice cover in the winter and lengthen the “growing” period in the summer for biological activity, including the growth of invasive plants and cyanobacteria blooms.

Although the surface of Lake Champlain froze over nearly every year in the early 1900s, it is now freezing much less frequently (Figure 13). Currently, the Lake freezes about once every four years; modeling suggests that by 2050, the Lake may freeze fully just once per decade (Figure 14).

Figure: Surface freeze-over of Lake Champlain
Figure 13 | Surface freeze-over of Lake Champlain
Figure: Probability of Lake Champlain surface freeze-over
Figure 14 | Probability of Lake Champlain surface freeze-over

Scientists continue to track the impacts of climate change as the Basin experiences more frequent intense storms in the spring and fall that increase erosion, dry spells in the summer that impact crops and increase the chance of wildfires, and milder winters that reduce ice cover. The warming climate impacts species diversity, habitat, and natural ecosystem function. Future winters may have shorter recreational seasons with limited ice fishing, and summers may be hotter with increased water quality impacts, thereby limiting recreational opportunities and other uses of the Lake.