Habitat fragmentation


Pepperwood and the Santa Rosa Junior College partner to offer a two-semester Bio 85 – Natural History of Pepperwood course that certifies participants as UC California Naturalists. Students have the option to submit an article for the Pepperwood Field Notes Blog as part of the course. The following is a student-submitted article.


Habitat Fragmentation

By Sophia Drucker, Spring 2017 Bio 85 participant

As human populations soar globally, our existence demands more and more resources; one of the foremost being space. In order to expand into that space, we develop our communities both in urban and rural settings. This expansion breaks up natural ecosystems and causes a phenomenon known as habitat fragmentation, where habitats are broken into smaller, more isolated pieces. Buildings are just one of the variables involved. Roads, agricultural lands with fencing, light, and even noise can disrupt ongoings within a delicate ecosystem.

There are many ways in which these fragmentations disrupt an ecosystem and its processes. One of the most obvious is population migration. Some species, like Caribou in Alsaka and Canada, travel hundreds of miles every year with the changing seasons. Busy urban centers and freeways create obstacles that interrupt migratory behaviors. Reproductive behaviors can be affected as well. If a population becomes segmented and adults cannot find one another for mating purposes, the gene pool is ultimately diminished. This not only happens in animals, but plants as well, especially those that rely on wind pollination. Another impact of fragmentation is a reduction of interior habitat. A 2015 study from the journal Science Advances showed that 70% of our remaining forests are within 1 kilometer of the forests’ edge. (Click here to read it.)

Sketch of how a corridor can connect open spaces by Sophia Drucker.

We’ve also managed to scare away or reduce populations of unwanted species that may be considered pests in our urban and agricultural spaces, but provide critical service to the habitat that they are native to. A good example is the vole, which provides critical tilling of the soil in grasslands and gives wildflower seeds a prime place to germinate. Without the human-caused reduction of voles, the makeups of our grasslands have greatly shifted.

While these types of human-caused fragmentation are considered detrimental, there is also habitat fragmentation that happens because of natural occurrences. This type of isolation tends to happen on a much larger scale and gives rise to some of the interesting evolutionary differences we see in species worldwide. An example in California is the prevalence of hardwoods—which are considered primarily eastern United States species—in our riparian habitats. These trees, including big leaf maple, California sycamore, white alder, and aspen, were separated from their eastern counterparts during the last ice age and have since evolved to the trees we know today.

Our understanding of habitat fragmentation has become much deeper in the last few decades, and scientists, environmentalists and conservation groups have made great strides in understanding and combating this phenomenon. Many groups have been fighting to put more acres of land into conservation and developers have been more cognizant of maintaining wildlife corridors. As with most conservation efforts, one of the most important ways we can contribute is through education. Pepperwood is a tremendous resource in this particular field.

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