EarthTalk: I read a heart-wrenching story of
a polar bear that swam 400 miles with its cub on its back
in search of an ice floe to rest on. It survived but its
cub did not. What can be done to save these magnificent
creatures? Is it too late?
—Jerry Bresnehan, Des Moines, IA
change is causing substantial amounts of offshore
sea ice to retreat at a record pace; it is a situation
that does not bode well for the future of polar
© Jupiter Images/Getty
sad but true that life is getting harder for polar bears
due to global warming. Polar bears live within the Arctic
Circle and feed primarily on ringed seals. The bears’
feeding strategy involves swimming from the mainland to
and between offshore ice floes, poaching seals as they come
up to breathe at holes in the ice.
climate change is heating up the atmosphere and substantial
amounts of offshore sea ice are melting. The result is that
bears must swim further and further out to sea in search
of ice floes; some expend all of their energy in doing so
and end up drowning. Scientists first noticed this deadly
phenomenon in 2004 when they noticed four drowned polar
bears in the Beaufort Sea off Alaska’s North Slope.
recently, researchers from the United States Geological
Survey (USGS) fitted several Alaskan polar bears with tracking
collars to find out the extent of their travels and document
how much trouble they are having hunting in a warmer Arctic.
One of the bears, a mother with a yearling cub on her back,
made what researchers are calling an “epic journey
in search of food” during September-October 2008.
“This bear swam continuously for 232 hours and 687
km and through waters that were 2-6 degrees C,” reports
USGS research zoologist George M. Durner. “We are
in awe that an animal that spends most of its time on the
surface of sea ice could swim constantly for so long in
water so cold.” During the rest of the two-month tracking
period, the bear intermittently swam and walked on ice floes
for another 1,200 miles.
while the mama bear survived the ordeal, she lost 22 percent
of her body fat during a crucial time of year for fattening
up before a long winter’s hibernation. And her cub
was not so fortunate. “It was simply more energetically
costly for the yearling than the adult to make this long
distance swim,” said Durner, whose findings were published
in the January 2011 edition of Polar Biology. The case of
this one polar bear and the failure of her offspring to
survive in the new environmental conditions of the Arctic
doesn’t bode well for the future of the species, especially
as Arctic sea ice continues to retreat at a record pace.
International Union for the Conservation of Nature (IUCN),
which maintains the international “Red List”
of threatened species, considers the polar bear “vulnerable”
due to climate change-induced retreating sea ice. For its
part, the U.S. government listed polar bears as “threatened”
in 2008 under the Endangered Species Act. The IUCN website
also points out that, while the polar bear has come to symbolize
the impact of global warming on wildlife, many other species
are similarly affected, including the ringed seal and well-known
species like the beluga whale, arctic fox, koala and emperor
argue that, since it is illegal to engage in activities
that could harm or kill threatened or endangered species,
Americans should be forced to cut their greenhouse gas emissions
to preserve polar bear habitat. While such a notion hasn’t
forced many of us to voluntarily drive fewer miles or turn
down our heat, it might be just what it will take the world’s
largest land carnivore from going the way of the dodo.
EarthTalk: What’s the nutritional difference
between the carrot I ate in 1970 and one I eat today? I’ve
heard that that there’s very little nutrition left.
Is that true?
—Esther G., Newark, NJ
fruits and vegetables are still our best source
of nutrients, those grown decades ago were much
richer in vitamins and minerals than the varieties
most of us get today. The main culprit in this disturbing
nutritional trend is soil depletion.
© Martin Poole, Digital Vision/Thinkstock
It would be overkill
to say that the carrot you eat today has very little nutrition
in it—especially compared to some of the other less
healthy foods you likely also eat—but it is true that
fruits and vegetables grown decades ago were much richer
in vitamins and minerals than the varieties most of us get
today. The main culprit in this disturbing nutritional trend
is soil depletion: Modern intensive agricultural methods
have stripped increasing amounts of nutrients from the soil
in which the food we eat grows. Sadly, each successive generation
of fast-growing, pest-resistant carrot is truly less good
for you than the one before.
A landmark study
on the topic by Donald Davis and his team of researchers
from the University of Texas (UT) at Austin’s Department
of Chemistry and Biochemistry was published in December
2004 in the Journal of the American College of Nutrition.
They studied U.S. Department of Agriculture nutritional
data from both 1950 and 1999 for 43 different vegetables
and fruits, finding “reliable declines” in the
amount of protein, calcium, phosphorus, iron, riboflavin
(vitamin B2) and vitamin C over the past half century. Davis
and his colleagues chalk up this declining nutritional content
to the preponderance of agricultural practices designed
to improve traits (size, growth rate, pest resistance) other
to breed new varieties of crops that provide greater yield,
pest resistance and climate adaptability have allowed crops
to grow bigger and more rapidly,” reported Davis,
“but their ability to manufacture or uptake nutrients
has not kept pace with their rapid growth.” There
have likely been declines in other nutrients, too, he said,
such as magnesium, zinc and vitamins B-6 and E, but they
were not studied in 1950 and more research is needed to
find out how much less we are getting of these key vitamins
The Organic Consumers
Association cites several other studies with similar findings:
A Kushi Institute analysis of nutrient data from 1975 to
1997 found that average calcium levels in 12 fresh vegetables
dropped 27 percent; iron levels 37 percent; vitamin A levels
21 percent, and vitamin C levels 30 percent. A similar study
of British nutrient data from 1930 to 1980, published in
the British Food Journal, found that in 20 vegetables the
average calcium content had declined 19 percent; iron 22
percent; and potassium 14 percent. Yet another study concluded
that one would have to eat eight oranges today to derive
the same amount of Vitamin A as our grandparents would have
gotten from one.
What can be done?
The key to healthier produce is healthier soil. Alternating
fields between growing seasons to give land time to restore
would be one important step. Also, foregoing pesticides
and fertilizers in favor of organic growing methods is good
for the soil, the produce and its consumers. Those who want
to get the most nutritious fruits and vegetables should
buy regularly from local organic farmers.
warns that just because fruits and vegetables aren’t
as healthy as they used to be doesn’t mean we should
avoid them. “Vegetables are extraordinarily rich in
nutrients and beneficial phytochemicals,” he reported.
“They are still there, and vegetables and fruits are
our best sources for these.”
of the American College of Nutrition; Kushi