278
evidence was even more dramatic:
across 53 plant species, leaves,
flowers, and fruits appeared almost
six days earlier in 2005 than they
had done in 1976. Similarly, the
fruiting season of 315 different
kinds of fungi studied in Britain
lengthened from 33 to 75 days in
the second half of the 20th century.
Longer plant growing seasons
sound like good news, but warmer
temperatures create problems as
well as advantages. Not all insects
are welcome, and shorter, milder
winters kill fewer dormant insects,
some of which may consequentlyundergo explosive population
increases and produce damaging
infestations. Warmer springs allow
pine sawflies, whose larvae eat
pine needles, to develop too rapidly
for the birds and parasites that feed
on them to keep their numbers in
check. Out of control, the sawflies
strip trees of their needles and
stunt their growth.Migration and hibernation
Birds that migrate in spring to
reach rich food sources also face
problems. Some have adjusted their
flight schedules to benefit from the
earlier abundance of insects. After
making the long journey from sub-
Saharan Africa, the first swallows
arrive in the UK about 20 days
earlier than they did in the 1970s,
and the first Bank Swallows reachSPRING CREEP
their destination 25 days sooner
than previously. However, there is
evidence that birds migrating from
Central America to New England in
the US have declined faster than
birds that remain in New England
all year. This is probably because
the migrant birds have been unable
to adjust their departure dates from
Central America to arrive in time to
benefit from the earlier abundance
of insects the way local birds do.
Climate change also appears
to have changed the behavior of
hibernating mammals. Zoologists
at the Rocky Mountain Biological
Laboratory found that yellow-
bellied marmots living in Colorado
emerged 38 days earlier in 1999
than they had done in 1975. In
2012, scientists at the University
of Alberta found that in the last two
decades, late snowfall has delayed
the emergence of the Rocky
Mountain ground squirrel from
hibernation by 10 days. This has
cut down the already short active
period in which they mate, give
birth, and feed to prepare for the
next hibernation cycle.Decoupling
Some organisms’ survival could be
threatened by the “decoupling” of
interactions between species. ThisWe are now sure of what we
only suspected years ago.
Policy needs to catch
up with science.
Camille ParmesanSome bee species now emerge earlier
in spring, in line with earlier flowering
dates for the plants that they pollinate.
Other bees, though, have not been able
to synchronize their emergence.US_274-279_Spring_creep.indd 278 12/11/18 6:26 PM