They argued that "understanding ecotype in relation to existing ecological constraints and releases may be more important than the taxonomic relationships between populations.

[9] The most recent decline at the turn of the 20th century caused much hardship for the Inuit and Cree communities of Nunavik, who hunt them for subsistence.

The subspecies of caribou (Rangifer tarandus), a medium-sized ungulate, inhabit boreal, montane and Arctic environments and "exhibit tremendous variation in ecology, genetics, behaviour and morphology."

[15] Current classifications of Rangifer tarandus, either with prevailing taxonomy on subspecies, designations based on ecotypes, or natural population groupings, fail to capture "the variability of caribou across their range in Canada" needed for effective species conservation and management.

[15] "Across the range of a species, individuals may display considerable morphological, genetic, and behavioural variability reflective of both plasticity and adaptation to local environments.

[3] According to the Québec's Natural Resources and Wildlife survey, the Leaf River herd (LRH) (Rivière-aux-Feuilles) had decreased to 430,000 caribou in 2011.

"[6] According to a National Geographic Daily News article, the George River caribou herd (GRCH) (Rivière-George) numbered only 3,500 animals in the late 1940s.

The Government of Nunatsiavut recommended that the "George River caribou calving grounds by designating a 14,000 km2 protection zone under the Regional Land Use Plan for the Labrador Inuit Settlement Area."

At the time of the accident, observers raised questions about Hydro-Québec's management of the newly built reservoir on the headwaters of the Caniapiscau River,[45] some 450 kilometres (280 mi) upstream, and focused their attention on decisions made in the days following the exceptionally heavy rains in September 1984.

The dead caribou drifting and beginning to accumulate along the eastern shore line of the Koksoak River were first noted by the residents of Kuujjuaq, but the cause of the deaths was not confirmed until a team of wildlife biologists and technicians from the Newfoundland-Labrador Wildlife Division arrived by helicopter to participate in a joint cooperative effort with the Québec Recreation, Hunting and Fishing Department to live capture and radio collar caribou swimming across the Koksoak River.

Coves and backwater were choked with the floating carcasses of dead caribou, with accumulations becoming increasingly larger in approaching the base of the Falls.

"[9] In a short analysis, Québec's Indian and Inuit Secretariat (SIGMAI) expressed the opinion that the fast-growing George River herd may have become accustomed to the reduced water flow from 1981 to 1984, during which time the reservoir was being filled.

SIGMAI hypothesizes that the caribou may have been surprised as the water flow of the Caniapiscau River was partially restored to its natural state in mid-September 1984, after the filling of reservoir had been completed.

The partial release of the headwaters back into the Caniapiscau was necessary because the power stations on the La Grande River could not yet turbine the full water flow.

According to Hydro-Québec, any major addition of water to the La Grande River would by necessity have been diverted around the power stations for months, even years, and seriously damage the floodgates which were designed for temporary use during exceptional climatic events.

Thus, SIGMAI chastised the Société d'énergie de la Baie James, a subsidiary of Hydro-Québec, that had just completed the construction of the reservoir, for not having planned to actively manage the restored water flow to the Caniapiscau River in such a way as to protect the caribou herd from exceptional floods caused by heavy rains or rapid spring thaw.

SIGMAI finally recommended that the water levels of the reservoir be lowered by about 0.5 metres (1 ft 8 in) for several months of the year to avoid the use of the flood gates during extreme rainfalls when the caribou are migrating in late summer and early fall.

This effect can be demonstrated by the northern front of forest harvesting in Ontario closely matching the southern boundary of continuous caribou occupancy.

This time lag is cause for concern, as there is overlap of forest harvest with the southern boundary of caribou range in Ontario.

Logging the mature boreal forest of northern Minnesota, Wisconsin, Michigan and Ontario has led to creeping aspen/birch habitat, followed by northward-moving white-tailed deer carrying the parasite Parelaphostrongylus tenuis.

[46] Woodland caribou persistence in Ontario will likely depend on the availability of large tracts of old growth forest situated at great distances from anthropogenic disturbance.

In addition, increased episodes of freezing rain in the winter may make it difficult for caribou to dig through the snow to reach their primary food source, lichens.

[47] The decline extended to the west as well and by 1980 only 25-30 animals persisted in northern Idaho and northeastern Washington; caribou had been extirpated elsewhere in the contiguous 48 states.

At that time, the entire woodland caribou population in the Selkirks consisted of one herd of 20-25 animals that occurred in extreme northeast Washington, northern Idaho and the Stagleap Park area of British Columbia (B.C.).

There is, however, a concerted effort on the part of the North Central Caribou Corporation and the Boundary Waters Canoe Area Wilderness to reintroduce a herd of around 75 animals from the Slate Islands in Lake Superior to northern Minnesota.