TOPICS IN BIODIVERSITY LOSS
 
Does Biodiversity Change? Is Biodiversity Changing Now? Biodiversity Loss and Humans
Future for Biodiversity What if Loss Occurs? What Can Be Done? Biodiversity Hotspots
     
 
Biodiversity does change through time. By that, we mean that the number of species present on Earth changes over time, and the composition of species changes as well. For example, there are no dinosaurs left on the planet today, but we know that at one point in the past they thrived. That is a change in biodiversity.

The most striking changes we see in biodiversity have come at mass extinctions. There have been five major mass extinctions through Earth’s history, which many smaller extinction events in between. In addition, there is background extinction; this is the term given to species extinctions that happen at a fairly regular rate at all times, and are not the result of a sudden natural disaster or impact event.

The figure below shows biodiversity through the Phanerozoic, the period of geologic time that includes today:
 
     
   
     
 

The grey section of the graph shows all genera, or groups of species, extant at a given time. The green shows the portion of those genera that are well-resolved, meaning scientists have a good understanding of the group, with few gaps. The yellow and red triangles show the “Big Five” and present-day mass extinctions, and the blue triangles show other large extinction events.

Click on the yellow and red mass extinction triangles to learn more!

 
     
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