what are the disadvantages of belt transects?

Answer 1

The main disadvantage I can see is that you are only getting a snapshot of the area at the exact time of the collection of information. Also, you are only getting information from the location of the area transected. It is usually a very limited section.

Another disadvantage is you can actually destroy the objects you are trying to measure as you collect the info.

One more problem to consider is the fallibility of the collectors.