Of all the things that surround us, landscape seems by far the most stable of all; when looking beyond the horizon, one might think that years will pass, people will come and leave, but the mountains in the distance will always remain in their places.
However, this stability is only an illusion; according to the research results, the process known as disturbance shapes the landscape greatly. Because of the disturbance process, the landscape, especially its forest elements, maintain relative stability and display amazing diversity.
As Turner, Gardner and O’Neill explain, “A disturbance is defined as a relatively discrete event that disrupts the structure of an ecosystem, community, or population and changes resource availability or the physical environment” (Turner, Gardner & O’Neill, 2001, 159).
Therefore, any event within the specific ecosystem that leads to the gradual change of the latter can be classified as a disturbance. There have also been attempts to define an ecosystem disturbance as tectonic movement, which actually matches the key idea of a disturbance.
However, it is essential to mention that a disturbance can be triggered not only by the movement of the tectonic blocks, but also by the factors that have much faster, though just as drastic effects, e.g., hurricanes, tsunami and storms.
All in all, “the definition of disturbance is scale dependent,” as Turner, Gardner & O’Neill (2001, 159) put it.
While the above-mentioned disturbance processes doubtlessly have huge effect on the lives of a number of organisms, as well as on the shape of the landscape, it is still important to figure out why these phenomena are considered of great significance for the landscape ecology.
Since disturbances do not happen often, their impact can be viewed as accidental and not quite long-lasting. Therefore, disturbances definitely deserve a better look.
The existing evidence shows that disturbances play a great role in shaping landscape: “Natural disturbances and those caused by human actions can promote plant and animal diversity by influencing the composition, age, size, edge characteristics, and distribution of stands across the landscape” (Voller & Harrison, 2011, 23).
Judging by the given statement, the effects of disturbances are not necessarily grandeur or induced by a cataclysm. At the same time, the patterns and scale of disturbance depends on the type of the landscape greatly, which makes disturbance and landscape mutually dependent.
One of the major positive aspects of disturbance, by the way, is its selectiveness; according to the research data, disturbances do not capture an entire area – instead, they seize a certain part of it, depending on their scale.
Thus, the positive effect of a disturbance is provided; once a disturbance could be observed in all corners of a specific area, the species within the given area would have been extinct, and the balance between certain elements of the landscape, e.g., the young and old segments of the chosen area would have been broken.
It is also noteworthy that disturbances pass relatively unnoticed in certain landscapes. On the one hand, it might seem that the disturbances on a grand scale must shape any landscape considerably; however, the specifics of certain areas make the landscapes greatly resilient to any sort of disturbance.
For example, in the places like desert, where the herbage is very scarce or completely absent, fires will not have a tangible effect.
As Turner, Gardner and O’Neill say, “Landscape position appears to influence susceptibility to disturbance when the disturbance itself has a distinct directionality (e.g., hurricane tracks) such that some locations are usually ore exposed than the others” (Turner, Gardner & O’Neill, 2001, 165).
Unlike one might have thought, disturbances are not chaotic; they have their own specific patterns that can be researched and, thus, predicted with sufficient precision. Depending on the specifics of the area, the patterns of disturbances may vary.
Among the most well known factors that influence the disturbance patterns the area of the patch must be named.
While a smaller area soon becomes completely engulfed by a certain disturbance, larger areas do not allow a disturbance to spread further; with many obstacles on its way, including mountains, canyons, rivers, etc., which actually make another factor, i.e., spatial distribution, a disturbance will most likely die out before it even reaches one third of the area.
Finally, frequency and recurrence interval must be taken into account.
While the latter means the mean time between the disturbance events and allows a specific area to renew and adapt to the changes brought on by the previous disturbance, the former is an approximate number of disturbances that happen in the given area within a certain amount of time (a year, as a rule) (Walker, 2011, 59).
Generally speaking, the process of disturbance influences the landscape ecology positively and changes the landscape very slowly, which allows the latter to change so that all its elements, including the fauna, could adapt to the new environment without considerable problems.
In addition, it is important to keep in mind that disturbances also characterize a landscape to a considerable extent.
Turner, M. G., R. H. Gardner, and R. V. O’Neill, 2001. Landscape ecology in theory and practice. Springer, New York, NY.
Voller, J. & S. Harrison, 2011. Conservation biology principles for forested landscapes. UBC Press, Vancouver, CA.
Walker, L. R., 2011. The biology of disturbed habitats. Oxford University Press, New York.