Читать книгу Fundamentals of Conservation Biology - Malcolm L. Hunter Jr. - Страница 81

The ecological interactions that are the basis of ecosystems are absolutely fundamental to life. Try to imagine a planet where dead things did not decompose, where water was not filtered through forests, or where plants did not replenish oxygen. Consequently, it is not really profound or insightful to say that ecosystems have ecological value. Nevertheless, it is extraordinary how often we try to place the well‐being of humanity over the well‐being of the ecosystems on which our lives ultimately depend.

Do all ecosystems have equal ecological value? No. Obviously, a large salt marsh will usually provide more ecological values than a small salt marsh, and, similarly, a dominant type of ecosystem such as spruce–fir forests will have more total ecological value than an uncommon type of ecosystem such as caves. Certain types of ecosystems may have a significantly greater importance to other nearby ecosystems than we would predict based on their area. We can call these keystone ecosystems, analogous to using the term keystone species for species with disproportionately significant ecological roles (Chapter 3; deMaynadier and Hunter 1997). The long narrow shorelines where aquatic and terrestrial ecosystems intersect are an excellent example of this (Fig. 4.7). Keystone ecosystems can also shape disturbance regimes that affect large areas by either inhibiting or facilitating the spread of a disturbance. To take two examples: a river can inhibit the spread of a fire, while certain types of woodlands that burn easily can facilitate the spread of fires to other ecosystems. Some of these keystone ecosystems are very small but have effects over large areas, for example, a cave that harbors a wide‐ranging colony of bats or a small pool that provides essential water for animals in a sizable landscape (M.L. Hunter 2017 ; Hunter et al. 2017; see Fig. 4.4).

Figure 4.7 The narrow riparian zones that border river shores are far more important ecologically, to both terrestrial and aquatic ecosystems, than you would predict given their narrow footprint. Thus they can be considered keystone ecosystems within a landscape. This is particularly evident in deserts where river shores are often a ribbon of green in an arid environment.

(Coconino National Forest/Public domain)