Intuitively, we tend to think of diversity in terms of numbers of species. However, this concept has been challenged in recent years.
Imagine the following: two ecosystems, each with three species. In the first ecosystem, there are two pine species and one spruce - a coniferous forest with all trees having about the same height, a dense evergreen canopy and no understory vegetation. The second ecosystem, has one pine, one maple and one fern species. In other words, one evergreen and one deciduous tree species with ferns in the understory.
Now, although species numbers do not vary between these two forests, most people would intuitively call the second one somewhat more diverse.
Do you agree? If so, how can we quantify this diversity?
In recent decades, unprecedented changes have impacted ecosystems all over the world causing habitat degradation and loss. The increasing occurrence of extreme climatic events (hurricanes, storms, floods) or the arrival of new insects and diseases (emerald ash borer, Dutch elm disease) are just a few examples of those changes.