Climate Change & Ecology

"Changes in climate are now affecting physical and biological systems on every continent.”
(Intergovernmental Panel on Climate Change, Fourth Assessment Report)

There is overwhelming evidence demonstrating the influence of climate change on ecological systems, ranging from large-scale ecological effects to disturbances on individual specie populations. While not all of the responses are negative, certain responses, such as population reductions, weight loss, and migration patters are alarming. Moreover, it is difficult to define and predict the interactive and evolutionary nature of ecological change, which may act to counter any beneficial ecological responses to climate change. It is still very early in the game relative to geologic time-scales. This makes long-term outcomes difficult, perhaps impossible, to determine.

The list below is a compilation of large scale ecological changes that have been documented in selected publications by Walther et al. (2002), Jenssen (2006), Parmeasean(2006), Stenseth et al.(2002), Jackson (2002) and Hassol (2004). The table highlights various species responses to climate change. Although the evidence provided is not comprehensive, it is enough to support the notion that climate change is impacting physical and biological systems across the globe.

Large-Scale Ecological Changes

Composition of and interactions within communities
Structure and dynamics of ecosystems
Species abundance
Species distribution, in particular migratory species distribution
Phenological and physiological changes
Upward range shifts of species
Animal size
Sex and age class of populations
More pronounced ecological effects are found in the Arctic, where average temperatures have risen at almost twice the rate of the rest of the world.
Longer growing seasons
Reduced sea ice
Reduced ice algae

Species response to climate change

Species	Response
*Plants*	Lengthening of growing season Increase in photosynthetic activity Early blooming Flowering and leaf unfolding occurring earlier
*Trees*	Advancement towards higher altitudes
*Fish*
Cod	Reduction in stocks
Sardine, Anchovy, Herring	During an El Nino event, upwelling of cold nutrient rich water off the coast of South America does not occur thereby killing off large populations.
Blue fin tuna	Changed migration and spatial distributions.
Krill	Reduced populations (which can cause a collapse of other marine species because Krill is a main food source)
*Arctic shrub*	Expansion of shrubs in previously shrub free areas
*Little auks*	When Atlantic flow water increases, auks are forced to find food in areas with suboptimal conditions
*Birds*	Breed earlier due to increased temperatures Earlier migration
Lowland birds	Extension of distribution from lower mountain slopes to higher areas
Mammals	Juvenile survival can be negatively affected
Seals	Reduced availability of areas for efficient feeding Reduced breeding Weight loss
Polar bear	Death and population decline Reduced possibility for hunting seals effects hunting success and survival
Soay sheep & red deer	Increased mortality during a positive NAO event- increased precipitation in Scotland wets the animal coat and thus reduces resistance to heat flux
*Reptiles*	Reproductive physiology Population dynamics
Amphibians	Earlier breeding Reproductive physiology Population dynamics
*Butterflies*	Earlier appearance Northward shifts

Additional stress will be placed on ecosystems as the human population continues to grow; urban sprawl, the need for agricultural fields, and the demand to create new jobs will destroy an increasing number of habitats. Species with low adaptability and/or dispersal capacity will likely be unable to find suitable habitats and die off.

While many of the documented ecological responses, such as longer growing seasons, early breeding and northward shifts may be beneficial to ecological systems, it is crucial to consider long-term effects and trophic interactions. Such effects may act to counter the benefits of favorable ecological responses by creating an entirely new set of problems for ecological systems.

Although these effects are not considered extensively in this project, one such example of a trophic interaction is the “mismatch hypothesis”. Often times, synchrony between predator and prey is crucial to the survival of the prey species (Stenseth, 2002).

Another alarming trophic interaction occurs when organisms low on the food chain die off, consequently making it difficult for predators to find food.

(Stenseth, 2002)