In yesterday's Loose Feathers, I linked to a story about how migratory birds have adjusted to climate change (or not, in some cases), according to the records at the Manomet research station. Basically, the short-distance migrants, like swamp sparrow, were able to adjust their schedules to keep pace with a warmer climate because the temperatures on their wintering grounds are pretty similar to the temperatures at Manomet, and follow similar cycles. Meanwhile, the long-distance migrants, like great-crested flycatcher, winter in the tropics and do not have the same temperature cues as a bird in the temperate zone. So they have not adjusted their schedules.
The reason this is important is that a warming climate is also changing what the birds will find when they get to their destinations. Consider the following two news reports, both issued yesterday.
First, the types of fish prevalent in Narragansett Bay and Rhode Island Sound have changed over the past fifty years.
According to Jeremy Collie, professor of oceanography at the University of Rhode Island's Graduate School of Oceanography, the fish community has shifted progressively from vertebrate species (fish) to invertebrates (lobsters, crabs and squid) and from benthic or demersal species -- those that feed on the bottom -- to pelagic species that feed higher in the water column. In addition, smaller, warm-water species have increased while larger, cool-water species have declined....Second, plants in Europe are climbing mountains at a rate of 29 m per decade.
"While we're catching more fish now, we're also catching smaller fish," said Collie, "and that corresponds with how the preferred temperatures of the fish here have changed. The fish community now is dominated by warm-water adapted species compared with what we started with, and fish that live in warmer water are smaller."
Collie added that fishing may also be a factor in the decline in fish size, since fishing removes the largest individuals from a population while leaving the smaller ones. However, he believes that climate is "the dominant signal." Sea surface temperature in the area of the trawls has increased by 2 degrees Centigrade since 1959, and the preferred temperature of the fish caught in the trawls has also increased by 2 degrees C.
Professor Lenoir, an ecologist at AgroParisTech, France, said the team wanted to establish whether "fingerprints of climate change were already apparent in ordinary ecosystems".These may serve as examples of how local ecosystems are changing rapidly in the face of warmer climates. Similar trends occur in phenomena more closely related to the timing of bird migration. A warmer spring may prompt plants to sprout, flower, and leaf more quickly. This in turn will affect any associated insects – either pollinators or leaf-eaters. The insects will either hatch and breed earlier, or keep to their schedules and have less to eat as a result.
In order to do this, the team of French and Chilean researchers compared the distribution of forest species between 1905 and 1985 with their distribution between 1986 and 2005....
"We used 171 species commonly found over French mountains, which are part of Mediterranean, temperature and mountainous forest ecosystems between 0m to 2,600m above sea level.
"We found a significant change in species' altitudinal distribution towards higher elevation of about 29 metres per decade.
"Out of the 171 species, most are shifting upwards to recover temperature conditions that are optimal for their development and reproduction."
Birds that time their migrations to take advantage of floral nectar (hummingbirds) or abundant insects (flycatchers and other insectivores) will find food scarcer than it used to be. Flowers and insects may already be past their peak by the time the birds arrive. Adjusting their migration schedules is absolutely crucial to their survival in a warmer climate.