Union membership in recent decades has been in stark decline. The picture has been particularly bleak over the past 20 years when it comes to young people.

Fewer than one in 10 workers under the age of 24 are now in a union, according to figures from the Office for National Statistics released on Thursday. The proportion of unionised 16- to 19-year-old workers has halved since 1995, from 6.4% to 3.2%, with a similar pattern among 20- to 24-year-olds.

But there are reasons for optimism: the same statistics also show a recent uptick in membership among young workers. In 2017-18, for 16- to 24-year-olds as a whole, the membership rate went up from 7.8% to 8.4%. Within this, for the 16-19 age bracket it went up from 2% to 3.2%.

Some people see the overall drop in membership as part of unions’ inevitable retreat into insignificance – casualties of a new, individualistic generation in a modern, flexible labour market that has no need for such outdated institutions.

But, as we have seen from the recent school strikes over the climate, young people are far from individualistic – they are prepared to take organised, collective action in the face of a crisis. If the 10,000 school strikers joined a union, then the number of members among 16- to 19-year-olds would increase by around one-third.

Fatalistic accounts of apathetic young workers ignore the structural changes in the world of work. Around a quarter of 16- to 24-year-olds are in low-paid, casual and insecure forms of employment – more than any other age group. Increasing levels of work casualisation present practical problems for unions in accessing and recruiting workers, issues that are amplified by hostile policymaking that has added to the barriers in taking industrial action.

Unions are well aware that they need to evolve their tactics and are beginning to make headway: the GMB union has gained recognition with online retailer Net-a-Porter and delivery firm Hermes, and the Independent Workers Union of Great Britain continues to recruit in the gig economy and among outsourced workers. Last year saw major action by McStrike campaigners as well as the largest equal-pay strike in UK history, involving 8,000 low-paid female workers in Glasgow.

The atmosphere in the US provides more reason for optimism. Despite an even more hostile policy environment than in the UK and overall declining union numbers, youth membership is increasing. In 2017, of the 858,000 net new jobs for US workers under 35, almost one in four was unionised. Some have attributed this growth to the increased precarity faced by young workers; other explanations focus on the rise in popularity of a new socialist agenda.

Similar ingredients exist here, and aspects of the ONS data suggest they could be beginning to influence membership numbers. And though younger workers have always been less likely to be in a union, their participation now is vital: climate breakdown and automation will drive seismic shifts in the world of work in the coming decades.

Unions are also trying to reflect the values of the younger generations by taking action on issues outside of the traditional workplace. The University and College Union became the first trade union to pledge support for the school students’ upcoming general strike on the climate, with others likely to follow. Calls for a cross-union campaign for a four-day week are also ramping up. In the US, initiatives such as Bargaining for the Common Good have explicitly brought together workplace demands with wider demands on issues of racism, debt and corporate power. A UK version could involve forging links with the renters’ unions that have emerged over the past year, recognising the significant wins this burgeoning movement has had already.

Trade unions remain the largest type of membership organisation in the UK. Enabling a younger, more transient workforce to find a collective voice and take on major problems such as the climate crisis and gender inequality with workplace action is no small task. But the opportunity to do so, it seems, could be here.

• Alice Martin is head of work and pay at the New Economics Foundation