It's not entirely accurate to say that two ecozones are *always* different. While they are often distinct, there can be overlap and even some shared characteristics. Here's a breakdown of how ecozones are usually differentiated:

Ecozones are defined by:

* Climate: Temperature, rainfall, and seasonal variations are key factors. A tropical rainforest ecozone will have very different climate conditions than a tundra ecozone.

* Geography: Elevation, landforms, and proximity to water bodies (oceans, lakes, rivers) all play a role. A mountain ecozone will have a different geography than a coastal ecozone.

* Flora and Fauna: The plant and animal life within an ecozone are adapted to its specific conditions. These are often unique to the ecozone, creating distinct ecosystems.

* Biogeographical History: The historical development of an ecozone, including past migrations of species and geological events, contributes to its unique characteristics.

Why ecozones can be similar:

* Transition Zones: Boundaries between ecozones are not always clear-cut. There can be transition zones where features of both ecozones are present.

* Shared Species: Some species may be found in multiple ecozones, particularly those with overlapping climate and habitat requirements.

* Human Influence: Human activities, such as agriculture, deforestation, and pollution, can alter the boundaries and characteristics of ecozones.

Overall, while there are often clear distinctions between ecozones, it's important to remember that they are dynamic systems and can exhibit some degree of overlap and change. The focus should be on the unique characteristics that define each ecozone rather than seeing them as completely separate and unchanging entities.