One in six jobs in Scotland's renewable energy sector could be lost within the next 12 months, according to an industry body.
Scottish Renewables said thousands of posts could go as a result of changes to UK government support schemes.
But it added that most firms feel positive about the future, with many having diversified overseas.
The UK government made a commitment at the general election to scrap onshore wind subsidies.
It said the renewables industry had been "a strong success in Scotland thanks to UK government support".
The Scottish Renewables poll found that its members predict of 16.9% decrease in full-time equivalent posts in Scotland over the next year.
Around 21,000 people are currently employed by the industry in Scotland.
Jenny Hogan, the group's director of policy, said government action was needed to give companies confidence to invest.
"Renewables are the largest source of power in Scotland, providing enough energy to meet more than half of our electricity needs, and the sector currently employs around 21,000 people here," she said.
"For Scotland's renewable energy industry to continue providing jobs and ever-greater reductions in carbon emissions, government must act quickly to give companies the confidence they need to keep investing in our sector."
Case study: Enercon UK
The wind turbine manufacturer and project developer employs 155 people in Scotland.
It expects its staff numbers to fall by up to a third over the next 12 months as employees move abroad to work in other countries where Enercon is active.
Country manager Richard Hatton said: "Government policy on onshore wind, leading to a much smaller market, reduced orders and a reduction in requirements for staff across the business."
Ms Hogan added: "These results show that changes to, and closures of, support schemes are having an impact on our members and on the numbers of employees within their businesses.
"The UK government is rightly excited about the economic opportunities presented by the impacts of the global shift to low-carbon energy, but it's really important we don't forget about the jobs in our renewable energy sector today.
"Onshore wind and solar are the two cheapest forms of electricity, but ministers are refusing to allow them to access long-term contracts for power, which will result in a marked slowdown in investment and a decrease in employment, as our survey has suggested."
A total of 46 companies took part in the anonymous survey. A total of 47% of those who responded felt either "positive or quite positive" about the future.
Ms Hogan said: "Obviously, many businesses in our membership are worried about the future and the lack of a business case for investment in parts of our sector.
"However, it is also clear that firms are working hard to diversify in many different ways, for example opening up overseas markets and moving into new areas such as energy storage and low-carbon heat."
Lang Banks, director of WWF Scotland, said: "These are worrying findings and underline the urgent need for the UK government to clarify its plans to support renewables and the thousands of people now employed in the sector.
"Scotland has incredible natural renewable energy resources, but if it is to maximise the economic opportunities on offer, the UK government must provide energy companies with a clear route to market.
"However, given we're part of the GB energy market, this is not just an issue for Scotland. As a net exporter of electricity, Scotland plays a key role in helping the whole of the UK in cutting its carbon emissions.
"If we are to be able to plug in to the cheapest and cleanest forms of power generation then it's vital our political leaders north and south of the border do all they can to support renewables."
A UK government spokesman said: "The renewables industry has been a strong success in Scotland thanks to UK government support, worth £730m per year.
"In our last funding round, over 40% of successful UK projects were based in Scotland."
The Scottish government's energy minister Paul Wheelhouse said: "We are determined to help support the sector in the face of destabilising, ill-judged policy changes made since 2015 by the Conservative UK government.
"Indeed, we have strengthened our own commitment in our draft Scottish Energy Strategy."