The Plaid Cymru motion also calls on the Welsh government to legislate to establish an independent environmental governance body for Wales.
There were 40 votes for the motion, no abstentions, and 13 voted against.
The Senedd is one of the first parliaments in the world to declare such an emergency, with the Scottish parliament having failed to do so last year when a similar motion was tabled in Holyrood.
Plaid Cymru member, Delyth Jewell, introduced the motion whilst referencing the missed UN Aichi targets on biodiversity: “When you miss a target like that, it doesn't stand still—that loss, that decline, continues apace. The situation gets worse.
“We now have an obligation to reset biodiversity targets and to back those up with investment, with plans for nature-based solutions, projects to centre on species recovery and changes that will prioritise healthy green and blue habitats across Wales.”
In support of the motion Labour member Mike Hedges said: “The danger is a dystopian future, with the only mammals surviving being pets, farm animals and scavengers such as rats.”
The Welsh Conservatives tabled two amendments during the debate, one of which called for the Welsh government to “work more closely with the UK government on the response to the climate emergency and nature recovery”.
However the amendment was blocked, with Jewell responding that whilst cooperation is vital on the issue of biodiversity loss, “this crisis cannot be tackled on a UK basis”.
She noted that the Environment Bill’s Office of Environmental Protection is for England and Northern Ireland only, adding that “we in Wales need to introduce our own primary legislation, our own governance structure”.
Nonetheless, in the Welsh government response, Julie James, minister for climate change said that whilst it would be supporting the motion and bringing forward legislation for an independent environmental governance body, “we'll be looking at those in the context of both the global framework, the UK framework, [...] to make sure that we do not have the unintended consequences of setting targets in a particular area that mean other very important areas are lost”.
Responding to the ‘historic step’, Annie Smith, co-chair of the Wales Environment Link biodiversity working group said: “This is a real landmark moment for nature in Wales.”
Katie-jo Luxton, RSPB Cymru director, also welcomed the move saying: “It was brilliant to see the motion to declare a nature emergency in Wales being passed last night.
“We urge the government to ensure nature’s recovery is treated with parity, and not compromised, in the push to achieve net zero.”
The State of Nature Report 2019 found that one in six species in Wales is threatened with extinction.
Dr Richard Benwell, CEO of Wildlife and Countryside Link described the emergency declaration as “great news for the Welsh environment” adding that both the Westminster and Welsh governments must ensure that targets in law guarantee domestic action meets international ambition, by setting a binding 2030 deadline to halt nature’s decline.
“As hosts of the COP26 talks this year wouldn’t it be amazing to see all four UK nations being the first in the world to set legal 2030 deadlines for nature’s recovery,” he added, “that would be true global leadership setting the benchmark for others to meet.”