stem used for decrease

I have come across a sentence where I am not sure if "stem" basically mean "decrease" or "increase". The sentence is

"The country is intervening in the currency markets once again to stem the appreciation of its currency in order to prevent further damage to its already struggling export sector."

I guess they want to deflate the currency to create better conditions for export but I am not sure.
Can you confirm ?

To stem = to stop (did you check the WR dictionary?)

http://www.wordreference.com/definition/stem :

stem2
▶verb (stems, stemming, stemmed)

• 1 stop or restrict (the flow of something).

Click to expand...

To stem = to stop/staunch/prevent the flow of (a liquid). Here, the rise in the value of a currency is seen as being like the flow of a liquid.

I must say that I am still a bit confused. I did check WR dictionary but it is not helping much in this case. I still think the meaning of stem here is to deflate the currency but none of the replies seem to confirm that.

"The country is intervening in the currency markets once again to stemthe appreciation of its currency =

"The country is intervening in the currency markets once again to stop the growth in value of its currency as compared to the currencies of other countries.

If something appreciates, it gains value.
To appreciate = to gain value

Compare with the converse:

Depreciate = to lose value.

'Stem' is a metaphor from liquid, usually water. It simply means 'stop' or 'restrain' the flow.
The classic situation is a boat which springs a leak.
If you put physical materials in place to block the leak or to narrow it down, then you are stemming the leak.
The phrase in the original post 'stem the appreciation of its currency' just means 'stop or slow down' the rise in value.
It does not say what measures are actually being used for this purpose.
It is not a technical economic term. It is stating the purpose, not the method.