Study Guide

Conservation Biology Themes

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  • Evolution

    All living things are shaped by evolution, but anthropogenic changes to habitats and ecosystems can happen faster than evolutionary change. Conservation biology has to take evolutionary processes into account. This means conserving genetic diversity, preserving land in a way that allows gene flow to happen.

    Part of the problem with losing populations of species, even if other populations exist, is the loss of genetic diversity. With fewer populations, inbreeding (individuals mating with relatives) can increase. Inbreeding can lead to reduced survival and reproductive success, a term known as inbreeding depression, and can lead to extinction.

    Experiments of lizards on Caribbean islands showed that small populations could increase their genetic diversity over several generations. Other research shows that they way humans interact with other animals has evolutionary consequences; Northeast Arctic cod have started maturing at younger ages because of fishing's selective pressure.

    Conservation biologists have developed breeding programs designed to increase genetic variation. The Florida panther was facing extinction because of inbreeding depression. Biologists developed a way of increasing genetic diversity in the Florida panther: breed Florida panthers with a different subspecies, the Texas panther. Conservation biologists were able to maintain the genetic identity of the two subspecies while increasing the genetic diversity of the Florida panther enough to save it from extinction.

    Fire is an evolutionary process. In some fire-adapted plants, seeds only open after a fire. Fire can also clear out competing plants, leaving more resources and space for fire-adapted plants. In North America, humans have historically suppressed fires because of the damage they can do to our worldly possessions. This allows understory plants to grow dense and leaf litter to accumulate, which can make wildfires worse.

    However, recognizing that fire is an important part of certain ecosystems, land managers have recently adopted the practice of "prescribed burns." You won't need aloe for these burns—they are controlled, small-scale fires that help restore ecosystems to their natural states. A benefit of small regular fires is that they burn up plant matter on the ground, reducing the fuel load for future, non-planned fires.

    Additionally, it would be a shame to lose genes that make a species better able to adapt to climate change, or protect against disease. By using conservation strategies that include evolutionary processes, biologists hope to maintain genetic diversity of the organisms on our planet.

  • Levels of Organization

    Most people talk about biodiversity in terms of number of species, but you can also think about it on different scales, from small-scale genes to large-scale ecosystems. Conservation can target genes, populations, species, habitats and ecosystems. How does conservation biology change for different levels of biological organization?

    Having protected areas like national parks is great, but knowing how big to make them is not always easy. After all, some animals travel long distances on a regular basis—elephants walk anywhere from a few miles to 50 miles a day, depending on food and water availability. Chimpanzees have large home territories that they defend as a group, and a protected area might not be able to include territories of two competing groups. Some animals, like sea turtles, travel the globe and return to one home beach to lay eggs. If that beach was turned into a resort, turtles won't be laying any eggs there.

    The number of individuals in a population might not reflect the amount of genetic diversity in that population. Over time, small populations lose genetic diversity—the more generations, the lower the overall genetic variation. Conservation biologists use a measure called the effective population size, an estimate of the number of breeding individuals in a population. Effective population size is often lower than the total number of individuals because old and young individuals do not mate; sex ratios can be skewed, and in plant and fungi populations, some of the individuals may be underground in the seed bank (plants) or not reproductive (fungi).

    Marine protected areas (MPAs) have developed from small-scale "no-take zones" or marine parks into networks of MPAs. Conservation biologists realized that fish and other marine animals do not stay in one place all the time. This is especially true of large marine animals that migrate or travel large distances looking for food and mates.

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