New figures have shown nearly 18 million litres of fuel have been used by three ferry services in the isles over the last five years.
A freedom of information request has shown that since 2015/16 the combined amount of fuel used by the services amounted to 17,606,448.
The figures are being used to signal a need for the rapid development of fixed link projects in order to help Shetland transition to a greener future.
Isles MSP Beatrice Wishart said: “Using millions of litres of fuel is not sustainable in our fight to tackle climate change.
“By building fixed links we can solve both reducing our carbon footprint while also improving connectivity across the islands.
“Fixed links are both the green and most effective solution when it comes to transforming Shetlands transport infrastructure. By having such infrastructure in place not only will this create super connected Shetland but will save literally millions of litres of fuel and by extension cut our carbon footprint significantly.
“Imagine a Shetland where someone who works in Lerwick but lives in Unst not being hampered by bad weather on their commute. Or imagine someone in Bressay being able to nip to the chemist in half the time. It is a realistic goal that we should work towards.
“We have had plenty of warm words but now is the time for action. I want to see action in the next Parliament for fixed links and that means the Scottish Government committing to giving Shetland the resources they need to evolve fixed links from a concept to tarmac. That is my ambition for Shetland.”