Basically, many economies suffer from the "Dutch Disease" where the easy profits in oil and gas crowd out all investment into other parts of the economy. The massive export economy props up the currency as well to the detriment of other exporting businesses.
When profitability is hurt by lower prices, these natural resources firms all pull back at the same time and there is no other industry that can take up the slack. The declining capital investment, jobs, and tax base all lead to pain..
If you look at it from the perspective of a city like Houston, where a big chunk of the local economy is driven by the oil industry, you can see why it's a big problem for some people.
When profitability is hurt by lower prices, these natural resources firms all pull back at the same time and there is no other industry that can take up the slack. The declining capital investment, jobs, and tax base all lead to pain..
http://www.economist.com/blogs/economist-explains/2014/11/ec...