Ecosystems

Ecosystems are more dynamic and ever changing than ever before, as a result of recent land use changes and deforestation, induced by humans. Suitably, it is necessary to study the influence these changes are having on plants, herbivores and higher up predators. Ecologists study herbivore populations, like insects such as Arthropods by looking at changes in populations from both a top down and bottom up approach. Insects have the potential to prey on plant species below them, but also can be preyed on by species such as insectivorous bats and birds. Two studies conducted by Bohm et. al (2011) and Morrison and Lindell (2012), demonstrate how birds and bats, as predators, play a substantial role in controlling the abundance of insects in populations. Interestingly, the studies also indirectly assess the notion that controlling insect populations by predation has the ability to control the quality of forests and the trees within them. While one experiment was conducted in a temperate forest, and the other in a tropical forest, both yielded that excluding birds and bats increased the abundance of insects, and therefore increased the amount of leaf damage.

Objectives & Methods:

Bohm et al. (2011) examined Schwäbische Alb and Hainich-Dün, two temperate forest regions in Germany over a span of two years. They randomly selected both young and mature oak trees to study how birds and bats influence the insect and plant populations. Oak trees were used as they tend to house different types of arthropods, insects Bohm et al. (2011) focused on in this experiment. Oaks abundant in arthropods are also not surprisingly abundant in bird and bat populations, since they feed on arthropods. 12 young and 8 mature were studied at the Schwäbische Alb ...

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...re experiments similar to these two in order to see how ecosystems will be affected in the future by human activity. The extinction of birds and bats from these two temperate forests would clearly cause distinct changes in these two ecosystems. Additionally, as Morrison and Lindell (2012) demonstrate, restoring damaged ecosystems is not enough; we need to make educated decisions in terms of how we restore the ecosystems. According to their study, planting trees in a plantation like fashion would attract more birds and bats, vital to maintaining a balanced forest ecosystem. Similarly, Bohm et al. (2011) confirm the notion that these predators are important, and need to be present in order to maintain this homeostasis. These two papers are vital to moving forward in the field of conservation in understanding the beneficial top down effects that predators can have.