![]() ![]() The term stability is often an umbrella term for many related ideas such as resilience, resistance, reactivity, and permanence ( Chen and Cohen 2001). The stability of a system 36 is a quantitative measure of how much it tends to stay the same in spite of external disturbances or changes in the state of the system. For that reason, we are interested in dynamics around equilibria. We tend to study the systems that stay around. As I type this sentence, I am at rest-at an equilibrium-because my attraction toward the ground due gravity is balanced by the repulsion of the floor in the opposite direction.Įcological systems are constantly changing but often stay around long enough for us to notice. The constant parts of our world often appear to be at an equilibrium, always on the verge of coming and going at the same time. That is, it lasts long enough for us to notice it in spite of processes that tend destroy it. Thus the world we experience reflects a sort of stability. This constancy exists in spite of forces that work against it - I eat to get the energy I need, and I don’t play in traffic. In spite of the dynamics of our lives, the world we experience shows some constancy over time - I was here yesterday and the day before, and I am still here today. I’m getting older, my cat is getting fatter, and the seasons come an go. They just provide different perspectives on the same processes.įeatures of our world are changing all the time. ![]() ![]() The above three representations of the same model show us that we can rearrange the letters and symbols many ways and yet still be the same model. Notice now that \(b\) or \(r\) can be negative, and \(b\) is independent of the the effect of the other species. Figure 5.1: Song Sparrow Melospiza melodia counts, \(N\), from 1966–2003 and the relation between observed counts ( \(N_t\)) and annual growth rate ( \(r_t = N_ ![]()
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