Greens senator Larissa Waters would make an "important announcement" at 1.30pm - the exact same wording as Scott Ludlam's career-ending "important announcement" the Friday before. Surely lightning couldn't strike twice, could it? Then again, the wags noted, Waters was born in Canada ... ha ha ha.

But the guffaws turned to sheer amazement when the senator fronted cameras outside Queensland Parliament House in Brisbane. With her baby daughter and partner watching on, Waters fought back tears as she apologised that after checking her situation in the wake of the Ludlam snafu, she had learned she was an unwitting dual citizen, too.

Section 44 of the Constitution had struck again.

Waters spoke of her devastation at the news, having wrongly believed that because she left Canada as an 11-month-old with her Australian parents, she needed to apply for Canadian citizenship. In a legal kick in the guts, her lawyers advised the law in Canada changed a week after she was born, requiring her to actively renounce the Maple Leaf.

"It is with a heavy heart that I am forced to resign as senator for Queensland," Waters said.

Coming just five days after Ludlam revealed he was a New Zealand citizen without knowing it, Waters' resignation was pure tragi-farce. How is it possible to be in your 40s and not know you are a citizen of another country? What kind of show are the Greens running here?

But zaniness and incredulity aside, this is a huge blow for the Greens. They have lost two of their best performers, who are both popular within the party and have a significant public profile beyond it. As one Greens member lamented, "they [the Greens] lost more than a fifth of the talent. And they lost more than a fifth of the profile".

While Waters led the Greens parliamentary fight on core environmental issues such as the Great Barrier Reef and the Adani coal mine and Ludlam was the party's passionate anti-nuclear spokesman, both co-deputy leaders also carved out non-traditional issues on which to appeal to voters.

As Attorney-General George Brandis struggled with envelopes, Ludlam actually understood what metadata is, and won a solid fan base through his campaigning against a mandatory internet filter and data retention. It says something about his efforts in this area that Julian Assange came to his defence, in the wake of his resignation.

No stranger to the snappy putdown, Ludlam was also a media-friendly figure. In 2014, he responded to a request to appear on journalist Chris Kenny's Sky News program, by tweeting "m8 i don't want this to sound harsh but the reason i won't be going on your show is that *nobody watches it*". In the same year, a speech he made to a near-empty Senate, asking Tony Abbott to rethink stereotypes about his [Ludlam's] home state of Western Australia ("understand you are closer to Denpasar than to Western Sydney") gained almost 300,000 YouTube views in three days.

Waters initiated parliamentary inquiries into domestic violence and gender stereotypes, including her much-publicised suggestion that girls and boys should be given more choice with toys than Barbies and trucks. More recently, she restarted the debate on the GST on tampons.

She has also made headlines as the first woman to breastfeed on the floor of Parliament, even moving a motion on black lung disease while feeding her baby daughter. It is hard to underestimate the message this sent about what working mothers can do.

The Greens won't necessarily lose any numbers in Parliament with Ludlam and Waters' departures. It's assumed that other Greens candidates will be able to take up their spots and keep the Senate group at nine and the overall partyroom at 10. But they are not so easily replaced.

Andrew Bartlett - tipped to take Waters' place - knows how the Senate works as a former Democrat senator and leader. But he does not enjoy the same profile and comes with some of his own baggage, following an abusive row with a Liberal senator in 2003. Twentysomething disability activist Jordan Steele-John - in line for Ludlam's seat - has no parliamentary experience.

As a Greens member noted, leader Richard Di Natale, Senator Sarah Hanson-Young and Melbourne MP Adam Bandt are now the only other federal Greens who are easily recognisable figures. This means it will be up to Di Natale, a clear and personable communicator, to pick up the slack. The Greens have a preference for delegating responsibility to portfolio holders, but this decentralised model may no longer work with a reduced talent pool.

There is time and space before next the federal election, due in 2019, for the party to rejig and recover. But losing Ludlam and Waters is much more than a quirky, embarrassing political event. Coming on top of the very public infighting with senator Lee Rhiannon, Di Natale said it best when he observed on Tuesday: "it's been a shocking few weeks, no sugar coating it".

Judith Ireland is a Fairfax senior writer.