The Market Vectors-Coal ETF (NYSEArca: KOL) has perked up in recent days and that is perhaps the most that can be asked of an exchange traded fund that has tumbled more than 48% over the past year. However, that slide could also be seen as a sign that things really cannot get much worse for KOL and coal stocks.

The coal industry is weakening as U.S. power plants switch to natural gas, environmental restrictions take hold and the world makes a stink eye at heavy greenhouse gas energy sources, reports Tom Randall for Bloomberg.

The ongoing shale oil boom has pressured natural gas prices and made natgas a cheap alternative to coal. Additionally, new environmental regulations have forced coal-fired power plants to close, and many are being replaced with natural gas.

Natural gas is starting to take over. According to the Energy Information Administration, natural gas represented 32% of U.S. electricity generation in April, compared to 30% from coal. Electricity generation from natgas has jumped 20% since  year-over-year while coal experienced a similar percentage plunge.

Moreover, China, the world’s largest consumer of coal, is beginning to diminish its reliance on coal in favor of alternative renewable energy sources as pollution becomes a major concern and clean energy becomes cheaper.