human caused or simply part of the natural order of things, there should be no denying that it is real. The Earth has seen numerous climactic changes over the years, such as the ice ages which turned the planet into seething masses of ice and snow (and with the most recent one technically continuing today)¹. However, it is the gradual warming of the planet which is concerning many scientists, particularly in regard to how it will affect biodiversity².
As greenhouse gases, such as carbon dioxide, absorb heat from sunlight, they prevent it from escaping back into space, thus causing the planet’s temperature to rise. Although temperature changes are perfectly natural, it is the speed of the changes which causes significant problems for species, as they have too little time to adapt.
One of the main impacts on biodiversity of climate changes is alterations in the timing of important seasonal life cycle events. For many species, the climate dictates stages in their life cycle such as migration and mating, with warming temperatures having significant impacts on numerous species³. For example, on the eastern coast of the US, warmer springs have caused several bird species to nest earlier, while birds and butterflies have both shifted their migration patterns, traveling earlier than they did in the 20th Century⁴⁵. The problem that arises from such changes is that they cause mismatches in the timing of breeding, impacting on survival and growth as species arrive at the wrong time to take advantage of their usual food supplies.
Another problem encountered by species as a result of climate change is that of range shifts⁶. The home ranges of most species are limited by their environmental tolerances, with for example the Rainbow trout (Oncorhynchus mykiss) requiring water temperatures of 0.0 °C – 29.8 °C⁷. Anything above or below this, and it will not survive. As global temperatures rise, many species are moving further northwards or higher in latitude to remain in an environment in which they can live. For example, 37 species of dragonfly have moved 30km northwards per decade in the UK, while several species of small mammal have shifted 50m per decade upwards in Yosemite National Park⁸. The question then arises, what happens when there is nowhere left to go? The answer unfortunately, is all too obvious.
As species move to take advantage of new habitats, the risk of diseases, pathogens and parasites spreading also increases and which can have serious ramifications for human health, fisheries and agriculture. For example, the oyster parasite, Perkinsus marinus, can cause serious die-offs in oysters. As a result of climate change, the parasite has extended its range by around 483 km (300 miles), from Chesapeake Bay to Maine, creating problems for local fisheries which rely on oysters for their livelihoods⁹.
Climate change also has some worrying effects on food webs. The food chain is a complex system which describes how species feed and rely on each other in order to survive. Take for example, the polar bear¹⁰. As the top predator, polar bears eat seals, which in turn eat Arctic cod. The cod feed on zooplankton, which themselves consume algae, which inhabit ice pockets. However, if rising temperatures cause ice to melt, then the algae will lose their habitat, leaving the zooplankton short of their preferred food and with the ripple effect running all the way up to the polar bears.
In many ways, the effects of climate change on biodiversity all converge on one thing: extinction. Species particularly at risk include animals adapted to mountain climates, such as the pika; animals reliant on sea ice, like polar bears; and cold water fish. Temperatures are already rising too quickly for many species, with evolution unable to keep up with the pace so we should start facing the facts: biodiversity is suffering, and the world is going to be poorer for it.