Question

Human use of fossil fuel is causing rapid global climate change. Will species adapt or become extinct as a result?  Is there any evidence that species populations are adapting, or failing to adapt, to contemporary climate change?

POSSIBLE THESIS STATEMENT

Answer 1

Worldwide, fossil fuels (oil, coal, and natural gas) dominate our energy consumption, accounting for 85% of all energy used. As mentioned previously, the rapid rise of fossil fuels is a relatively recent phenomenon, developing in the nineteenth century with the discovery of oil and the industrialization of economies, and expanding rapidly in the twentieth century with increased economic development and rising populations and affluence.Burning fossil fuels releases about 8.5 billion tons of carbon (as CO₂) into the atmosphere each year, causing its concentration to increase and Earth’s greenhouse warming to strengthen, which leads to rising global air temperatures. Since 1880, average global air temperature has risen approximately 0.9°C.

The rise of pollution corresponds to the increased use of petroleum in the twentieth century, as new synthetic products such as plastics, pesticides, solvents, and other chemicals, were developed and became central to our lives. Many air pollutants, including nitrogen and sulfur oxides, fine particulates, lead, carbon monoxide, and ground-level ozone come from coal and oil consumption by power plants and automobiles. Heavy metals, such as mercury, lead, cadmium, and arsenic, are produced from mining, the burning of fossil fuels, and the manufacture of certain products like metals, paints, and batteries.

Human alterations to the environment are causing some species to become evolutionarily adapted to new conditions. Because people generally harvest large plants and animals that often produce the most offspring, selection favors early reproductive maturity and organisms with smaller body sizes. This could lead to lower reproduction, species fitness, and cause populations to decline faster than expected. Other long-term studies of bird populations offer insights into how climate change affects fitness. As temperature warms and spring comes earlier in the year, insect populations (a food source for birds) peak sooner, creating a selective force on bird populations that favors individuals who lay their eggs earlier in the year. Studies testing this hypothesis have found that some bird populations do not adapt egg laying to warming, leading to lower fitness, whereas other studies have found rapid changes in egg laying that keep up with shifting insect populations. Some scientists argue that many species will not be able to adapt fast enough to new environmental conditions, possibly leading to 15–37% of species going extinct

Human-altered environments are often characterized by deliberate or accidental changes in species interactions. Food webs are intricate feeding relationships, and when the abundance of one species increases or decreases, this change has the potential to ripple throughout the rest of the community. For example, the introduction of a new species, such as a predator, can have detrimental effects to communities with species that have evolved in the absence of predators. The brown tree snake is an example of a particularly devastating species that was accidentally introduced to the Pacific island of Guam following World War II. Within decades of introduction, this species drove half of the native reptiles, two thirds of the mammals, and three fourths of the bird species to extinction.

Less-dramatic changes in food webs can occur with changes in species abundance. For example, in the Yellowstone National Park region (Wyoming, US), settlers in the nineteenth century extirpated wolves to make way for cattle ranching. The removal of one of the apex predators in the community initiated what is called a “trophic cascade.” Wolves in this region feed on herbivores like elk and moose. With the loss of predators, the herbivore population exploded, causing them to over browse one of their primary food sources — willow trees. The resulting decline in willows had a negative impact on two thirds of the bird species that used willows for nesting and perching. Thus, changes at the top of the food web tricked down through the rest of the community, with unanticipated impacts on trees and birds. Interestingly, restoration of the Yellowstone ecosystem through the reintroduction of wolves in the 1990s has reversed many of these changes. In tropical regions, decreasing forested habitat has been shown to eliminate top predators that need large home ranges for acquiring food, thereby setting off similar trophic cascades whereby herbivores become abundant and the plant community is negatively affected.

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