A climate emergency has been declared by Chichester City Council after being on the agenda since December last year.
The decision was made at a city council meeting on Wednesday night (June 19).
Green councillor Sarah Sharp, who proposed the motion back in December, said: "I am hugely relieved that the Council has agreed to back this climate change motion. Working together with our colleagues will be key over the coming months.
"There are a huge number of good ideas out there for planting trees, working with schools and writing to Parliament and the MP so that enough money is provided to local councils to carry out the changes needed. People from all political backgrounds are taking this seriously.
"There is a recognition that are things we can do as individuals but there are bigger things we will have to do together - for example making sure that safe cycle ways get put in and people on low incomes are supported with insulating their houses - these things can't be done by individuals and that is why we need to act as councils to enable our residents to live more sustainably.
"The changes we make to cope with climate change must improve the lives of the many and climate change should not be something just for the rich who have enough money to think about this"
The motion for the reduction of single use plastics was also passed at the same meeting. Plans include promoting deposit schemes and looking into expanding community use of Terracycle.
Cllr Sharp added: "There is so much still needing to be done to reduce our reliance on plastic. But we are talking about these issues now. We just need to keep on talking and carrying these conversations through to our MP and Parliament that can make the real changes that manufacturers will need to take on board.
"Even our Market stallholders are telling me they are keen to get on board with this. Perhaps Chichester could have a plastic-free market?"