Avian malaria found in Alaskan birds, another indication of climate change

A form of malaria that infects birds has been found in parts of Alaska, and scientists say the discovery is another indication of climate change in the north.

Common redpollThe spread could prove devastating to arctic bird species that have never encountered the disease and thus have no resistance to it, said San Francisco State University Associate Professor of Biology Ravinder Sehgal, one of the study’s co-authors. The study was published Wednesday, Sept. 19, 2012 in the journal PloS One.

The avian malaria parasite is related to the human form and so the bird study could help scientists track how climate change is affecting human malaria.

Researchers examined blood samples from both resident and migratory birds collected at four sites from 61°N to 67°N, with Anchorage as a southern point, Denali and Fairbanks as middle points. Coldfoot was the northern point, roughly 960 kilometres north of Anchorage. They found infected birds in Anchorage and Fairbanks as far north as 64°N, but not in Coldfoot

In migratory birds, samples were taken from both adults and hatchlings to see if the infection had occurred locally or during migration.

The study notes that the infected birds at 64°N were above the Arctic Circle commonly known to people across the region as “north of 60”)

Using satellite imagery and other data, researchers were able to predict how environments will change due to global warming — and where malaria parasites will be able to survive in the future. They found that by 2080, the disease will have spread north to Coldfoot and beyond.

“Right now, there’s no avian malaria above latitude 64 degrees, but in the future, with global warming, that will certainly change,” Sehgal said. The northerly spread is alarming, he added, because there are species in the North American arctic that have never been exposed to the disease and may be highly susceptible to it.

“For example, penguins in zoos die when they get malaria, because far southern birds have not been exposed to malaria and thus have not developed any resistance to it,” he said. “There are birds in the north, such as snowy owls or gyrfalcons, that could experience the same thing.”

Researchers are still unsure how the disease is being spread in Alaska and are currently collecting additional data to determine which mosquito species are transmitting the Plasmodium parasites that cause malaria.

The data may also indicate if and how malaria in humans will spread northward.

Modern medicine makes it difficult to track the natural spread of the disease, Sehgal said, but monitoring birds may provide clues as to how global climate change may effect the spread of human malaria.

The study is the fact that the malaria parasites were able to complete their transmission cycle in the North American Arctic” provides “empirical evidence that local hosts in the north of Alaska may be exposed to new parasites with impending global warming,” especially if there is increased variation of both day/night and season temperature changes. Rainfall is also a factor.

Both Anchorage and Fairbanks are likely to have suitable conditions for the avian malaria parasite “completion, other areas with high annual precipitation but mild precipitation and temperature seasonality would be predicted to also be suitable” for the parasite.

One form of the avian malaria parasite has been previously in four bird species: the Common Rosefinch (Carpodacus erythrinus) in South Korea, the Greater Scaup (Aythya marila), the Pacific Golden Plover (Pluvialis fulva) and the Common Yellowthroat (Geothlypis trichas) in the United States, and in six migratory species, meaning that form can tolerate cold temperatures.

The book Birds of British Columbia says the Greater Scaup is a common migrant on the BC coast and may winter in BC, and an abundant migrant in the BC interior in both spring and fall, and often winters in the Okanagan.  The Pacific Golden Plover is rare in BC, because its migration route takes it toward the east coast.  It is usually spotted in the Peace River region but has been seen occasionally near Massett and Boundary Bay. The Common Yellowthroat can be found through the BC mainland in the summer but is rare on Vancouver Island and Haida Gwaii.

A study in New Brunswick has shown that one form of mosquito that tolerates cold infects birds in that province. Although that mosquito is “rare” in Alaska, a close relative is common in the state and although the scientists were unable to find the source of the infection, that Alaskan mosquito could be a prime suspect.

 

Letting salmon escape from nets could benefit grizzly bears and even the fishers, study says

Grizzly eating a salmon
A grizzly bear eats a salmon. A new study says managers must consider the value of salmon to the entire ecosystem. (Jennifer Allan)

A new study suggests that the health of the grizzly bear population is also a strong indicator of the health of Pacific salmon—and perhaps surprisingly, allowing grizzlies to consume more salmon will, in the long term, lead to more, not less, salmon.

The study, led by Taal Levi, of the University of California at Santa Cruz and colleagues from Canada, suggests that allowing some more Pacific salmon to escape the nets of the fishing industry and thus spawn in coastal streams would not not only benefit the natural environment, including grizzly bears, but could also eventually lead to more salmon in the ocean. Thus there would be larger salmon harvests in the long term—a win-win for ecosystems and humans.

The article, “Using Grizzly Bears to Assess Harvest-Ecosystem Tradeoffs in Salmon Fisheries,” was published April 10 in the online, open-access journal PLoS Biology. In the study  Levi and his co-authors investigate how increasing “escapement”—the number of salmon that escape fishing nets to enter streams and spawn—can improve the natural environment.

“Salmon are an essential resource that propagates through not only marine but also creek and terrestrial food webs,” said lead author Levi, an environmental studies Ph.D. candidate at UCSC, specializing in conservation biology and wildlife ecology.

Salmon fisheries in the northwest Pacific are generally well managed, Levi said. Managers determine how much salmon to allocate to spawning and how much to harvest. Fish are counted as they enter the coastal streams. However, there is concern that humans are harvesting too many salmon and leaving too little for the ecosystem. To assess this, the team focused on the relationship between grizzly bears and salmon. Taal and his colleagues first used data to find a relationship between how much salmon were available to eighteen grizzly bear populations, and what percentage of their diet was made up of salmon.

The study looked at Bristol Bay, Alaska, the Chilko and Quesnel regions of the Fraser River watershed and Rivers Inlet on the Inside Passage, just northeast of northern Vancouver Island.
The study says adult wild salmon are “critical” to ocean, river and terrestrial ecosystems. As well as humans, salmon are eaten by orcas, salmon sharks, pinnipeds (seals and sea lions). On land, salmon are eaten by black and grizzly bears, eagles and ravens.

Because the grizzly is the “terminal predator” the study says “if there are enough salmon to sustain healthy bear densities, we reason there should be sufficient salmon numbers to sustain populations of earlier salmon-life history predatory such as seabirds, pinnipeds and sharks.”
As is well known in the northwest, the study says “bears are dominant species mediating the flow of salmon-derived nutrients from the ocean to the terrestrial ecosystem. After capturing salmon in estuaries and streams grizzly bears typically move to land to consume each fish, distributing carcass remains to vertebrate and invertebrate scavengers up to several hundred metres from waterways.”

“We asked, is it enough for the ecosystem? What would happen if you increase escapement—the number of fish being released? We found that in most cases, bears, fishers, and ecosystems would mutually benefit,” Levi said.

The problem, the study says, is that fisheries management have a narrow view of their role, what the study calls “single-species management,” concentrating on salmon and not the wider ecosystem. “Currently,” the study says, under single-species management, fisheries commonly intercept more than 50 per cent of in bound salmon that would otherwise be available to bears and the terrestrial and aquatic ecosystems they support.”

The relationship between salmon and bears is basic, Levi said. “Bears are salmon-consuming machines. Give them more salmon and they will consume more—and importantly, they will occur at higher densities. So, letting more salmon spawn and be available to bears helps not only bears but also the ecosystems they nourish when they distribute the uneaten remains of salmon.”

When salmon are plentiful in coastal streams, bears won’t eat as much of an individual fish, preferring the nutrient-rich brains and eggs and casting aside the remainder to feed other animals and fertilize the land. In contrast, when salmon are scarce, bears eat more of a fish. Less discarded salmon enters the surrounding ecosystem to enrich downstream life, and a richer stream life means a better environment for salmon.

In four out of the six study systems, allowing more salmon to spawn will not only help bears and the terrestrial landscape but would also lead to more salmon in the ocean. More salmon in the ocean means larger harvests, which in turn benefits fishers. However, in two of the systems, helping bears would hurt fisheries. In these cases, the researchers estimated the potential financial cost—they looked at two salmon runs on the Fraser River, B.C., and predicted an economic cost of about $500,000 to $700,000 annually. This cost to the human economy could help support locally threatened grizzly bear populations, they argue.

While these fisheries are certified as sustainable by the Marine Stewardship Council (MSC), the researchers suggest that the MSC principle that fisheries have minimal ecosystem impact might not be satisfied if the fishery is contributing to grizzly bear conservation problems.
The researchers believe the same analysis can be used to evaluate fisheries around the world and help managers make more informed decisions to balance economic and ecological outcomes.

 

What do grizzlies eat in northwestern BC ?

The current study and previous studies track the grizzly’s diet by studying the nitrogen and carbon istopes in grizzly hair. In one study in the early part of this decade, the BC Ministry of the Environment used guard hairs from “passive hair snags” as well as samples from bears killed by hunters or conservation officers.

The 2005 study says “Guard hairs are grown between late spring and fall, thus integrating the diet over much of the active season of temperate-dwelling bears.” Analysis of the isotopes can show what the bears ate over the season.

The study identified four elements in the grizzly diet across British Columbia, Alaska, Yukon and the Northwest Territories: plants, “marine-derived nutrients” mostly salmon, meat (primarily from ungulates such as moose) and in inland areas, kockanee salmon.

As could be expected, grizzly salmon consumption is highest in coastal areas. Males generally consume more salmon than females, likely because a mother grizzly may avoid taking salmon if there is danger to the cubs from males. The further inland a grizzly is found, salmon is a lesser factor in the bear’s diet. In Arctic regions, grizzlies can feed on arctic char, whales, seals and barren-ground caribou.

So what do local grizzlies eat? (excerpts from the 2005 study, Major components of grizzly bear diet across North America,  National Research Council Research Press  published March 28, 2006)

Map of grizzly diet and salmon
Grizzly consumption of salmon on the northwest coast (NRC)

North Coast 54.54 N 128.90 W (north and west of Kitimat)
Plants 33 per cent Salmon 67 per cent

Mid Coast 52.50 N 127.40 W (between Bella Bella and Ocean Falls)
Plants 58 per cent Salmon 42 per cent

Upper Skeena Nass 56.80 N 128.80 W
Plants 71 per cent Salmon 5 per cent Meat 13 per cent

Bulkley Lakes 54.10 N 127.10 W
Plants 63 per cent Salmon 6 per cent Meat 16 per cent Kokanee 15 per cent

Cranberry 55.40 N 128.40 W (near Kiwancool)

Plants 30 per cent Salmon 17 per cent Meat 40 per cent Kokanee 13 per cent

Khutzeymateen 54.68 N 129.86 W (near Prince Rupert)
Plants 22 per cent salmon 78 per cent

 

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Other authors of the 2010 study are Chris Darimont, UCSC, Misty MacDuffee Raincoast Conservation Foundation, Denny Island, BC; Marc Mangel, Paul Paquet, UCSC and University of Calgary, Christopher Wilmers, USCC
Funding: This work was funded by an NSF GRF and Cota-Robles Fellowship (TL), a NSERC IRDF (CTD), the Wilburforce and McLean Foundations, and Patagonia. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

2005 study by Garth Mowat Aurora Research  Crescent Valley BC and  Douglas Heard BC Ministry of the Environment, Nelson