There are two issues with this word. The first is that it is commonly misspelled as DIRTH.
The second issue is the more egregious. Have you ever heard something like this?
There is such a dearth of sand on this beach!
Many seem to think that DEARTH means “a great amount of.” It’s actually the opposite! The word DEARTH means a scarcity of or an inadequate supply. A more appropriate sentence would be something like …
There is such a dearth of snow on this beach!
One way to remember the correct meaning is that scarcity makes something DEAR to you. So, DEAR = DEARTH. It’s also the opposite of PLETHORA, which means an overabundance.
Try this analogy –
PLETHORA : TOO MUCH :: DEARTH : _______________.