The global push to combat climate change has brightened the investment outlook for low-emissions industries, but some hedge funds are ramping up negative bets on solar energy and electric car firms they see as vulnerable to competition from cheaper oil.
Financial data firm Markit said on Tuesday that 'short interest' - which measures the number of shares lent to speculators betting on a fall in those stocks - had reached record high levels on some key companies in the solar energy and renewables sector.
More than 150 world leaders met at United Nations climate change talks in Paris on Monday in the hope of reaching a deal to hold back the Earth's rising temperatures.
Markit said short interest levels had risen to all-time highs at Solarcity and SunEdison, and had been climbing in the Guggenheim Solar Exchange Traded Fund (ETF) , which includes Solarcity and SunEdison in the fund.
Markit added that hedge funds had also increased their short bets on electric car manufacturer Tesla Motors and Spanish renewable energy company Abengoa, which has started insolvency proceedings.
Investors said a drop in the price of oil had made it harder for electric cars to compete in terms of costs with traditional vehicles and had also put pressure on prices in the solar sector.
"Solar prices have plummeted and there's no incentive in buying a Tesla when the oil price is so cheap," said Clairinvest fund manager Ion-Marc Valahu.
In order to profit from a stock falling, short sellers can borrow the stock and sell it, expecting it to drop in value so they can buy it back at a lower price and pocket the difference.
According to Markit, the level of short interest on the Guggenheim Solar ETF stands at 7.3 percent - around three times the average for companies in the benchmark U.S. S&P 500 index .
The Guggenheim Solar ETF is down 20 percent so far in 2015, while Solarcity shares are down by nearly 50 percent and SunEdison is down by more than 80 percent.