Wednesday’s cancellation of Minnesota moose hunting for 2013, and almost certainly for years to come, underscores the continuing free fall of a species that some would call a walking emblem of our boreal forests and bogs.
By coincidence, it also fits neatly into a national narrative laid out in the past week by the National Wildlife Federation in its new report, “Wildlife in a Warming World.”
In 48 engagingly written, usefully illustrated pages, NWF’s scientists offer a sweeping survey of how scores of animals (and plants, and whole ecosystems) are faring in this time of changing climate.
Minnesota’s declining moose population gets prominent mention as just one example of climate impacts whose cause can no longer be denied, but yet resists the level of detailed understanding that could yield solutions:
Warming is particularly problematic for moose in northern Minnesota. The moose population in the northwestern part of the state plummeted from about 4,000 animals in the mid-1980s to less than 100 animals by the mid-2000s.
Biologists attribute most of this decline to increasing temperatures: when it gets too warm moose typically seek shelter rather than foraging for nutritious foods needed to keep them healthy. They become more vulnerable to tick infestations, which have proliferated as the region has warmed.
Ticks leave moose weakened from blood loss and with hairless patches where they tried to rub off the ticks. Without protective hair, these animals can die from cold exposure in the winter. Individual moose infested with 50,000 to 70,000 ticks — ten to twenty times more than normal — have been documented.
35% mortality in a single year
The Minnesota Department of Natural Resources’ intensive effort to investigate these new patterns of moose mortality has been reported here and elsewhere in recent weeks.
And yet even the DNR appears to have been taken somewhat by surprise when the results of its annual aerial survey came in last week, indicating a 35 percent drop in the moose population in a single year. Rather than wait for the numbers to reach the tipping points set in its moose management plan, the agency faced the inevitable and ordered an immediate halt.
Extensive radio-collaring and quick-response forensic investigation will continue (continuous updates, with cool photos and videos, are offered here). But it is frankly difficult to imagine just what can be done to shield the Arrowhead region’s 2,700 surviving moose from such a complex interaction of climate and parasites, let alone restore a population that approached 9,000 just seven years ago.
As you might expect, moose are also in trouble in the few other portions of the U.S. where any are left at all, including some areas where moose were essentially gone until fairly recent, still tenuous recoveries. NWF’s Wildlife Promise blog offered this observation yesterday:
Moose were once found as far south as Pennsylvania before over-hunting and habitat destruction wiped them out from much of the eastern United States. Populations in places like Massachusetts are still re-establishing a foothold.
But in New Hampshire, the impact of warmer temperatures on moose are clear and dire. Researchers say New Hampshire moose are literally being eaten alive by ticks. Moose there have to deal with 30,000 ticks at a time in a normal year, but in recent warm years, moose carry as many as 150,000 ticks.
The moose die of anemia, a lack of healthy red blood cells. After the unseasonably warm winter in 2011, they think that it’s likely that all calves born the previous year were killed along with 40 percent of adults.
NWF acknowledges that many of the impacts surveyed in “Wildlife in a Warming World” aren’t news per se. The point of this report is to assemble them into a coherent whole and, by doing so, to make the overall patterns more visible.
Breakup of ecosystems
And the patterns are not so simple (as some folks apparently still assume) as, say, Iowa’s environment slowly but cohesively edging into Minnesota, and Minnesota’s moving on to Manitoba intact:
As climate change alters the playing field, plants, fish, and wildlife face new situations, with sometimes surprising outcomes. Individual species respond differently to changes in the timing of seasons or the frequency of extremes, which can create mismatches between animals and their food sources.
At the same time, the ranges of some species are shifting at different rates, creating interactions among species that previously did not coexist. All these shifts will create winners and losers, but ecologists expect that climate change will bring an overall decline in biodiversity.
Shifting ranges for pests and disease-causing pathogens may have some of the most devastating impacts for wildlife and habitats. For example, warming ocean waters have enabled the outbreak of microbial disease in reef-building corals and pathogens of the eastern oyster. Mountain pine beetle outbreaks decimated trees on more than 26.8 million acres in western North America from 1997-2010.
Already there is evidence that climate change is causing declines in species populations and localized extinctions. For example, local extinctions of desert bighorn sheep populations in California are strongly correlated with climate conditions, especially declines in precipitation that reduce food availability.
Everyone who reads this report will find examples that resonate personally and profoundly. For me, after the moose, I guess the item that will register the longest concerns the huge sturgeon die-off in Iowa this past summer, just one among the many fish kills that are growing larger and more frequent as a consequence of climate change.
The combination of heat and drought is particularly challenging for freshwater fish. When streams get too warm, fish growth rates decline and stressed fish become more susceptible to toxins, parasites, and disease. The lower water levels during drought cause the water temperatures to rise more rapidly and reach greater extremes. Warm water holds less oxygen and facilitates the rapid growth of harmful algae.
During the summer 2012 drought, the stench of rotten fish was common across rural and urban areas alike as fish died by the thousands. Nearly 58,000 fish, including 37,000 sturgeon with a market value of nearly $10 million, died along 42 miles of the Des Moines River.
Survivor of lost worlds, till now
I’m not an avid sturgeon angler, although I have had some opportunities to view them close up and with awe. What moved me on reading this passage was to think, well, here’s a species that has survived more or less unchanged since the late Cretaceous period.
That’s more than 65 million years of adaptation to changing climates, including the shifts that drove mass extinctions of dinosaurs and marine reptiles to mark the end of the Cretaceous chapter in Earth’s history.
And yet even the sturgeon would seem to be vulnerable, in very large numbers, to the pattern of changes we’ve set in motion in this Anthropocene period, chiefly by burning fossilized remains of the sturgeon’s former worlds.