A tension zone is a transitional zone between two distinctive zones, the zones may be influenced by climatic

Climate

Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

 factors, and geologicalvariation. creating a floristic

Flora

Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...

 tension zone.A marine tension zone may be affected by variables such as depth, climate or salinity.In a tension zone there is the increased probability of hybridization between species of the separate zones and thus the tension zone may also be a hybrid zone

Hybrid zone

A hybrid zone exists where the ranges of two interbreeding species meet. For a hybrid zone to be stable, the offspring produced by the cross have to be less fit than members of the parent species, although this condition does not need to be met in the very first hybrid generation...

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Historically tension zones were entirely natural in origin, however human activity has altered the tension zones in a variety of areas all over the world.