THE EU is struggling with the biggest set of challenges in its history: from the refugee crisis to the eurozone’s difficulties, from Putin and Ukraine to anti-democratic trends in Hungary and Poland to Brexit.

Scotland’s clear vote to stay in the EU is a positive light in the broader gloom, leading to a much more positive mood towards this country in Brussels and beyond. But while Theresa May struggles to define what Brexit is, and Nicola Sturgeon holds back those wanting an early second independence referendum, Scotland cannot simply put EU choices on the back-burner.

The EU will not wait for Scotland, and choices now will impact on what sort of European future Scotland has. Theresa May will probably trigger Article 50 in early 2017, starting exit talks for the UK. An exit deal should be done within two years but not a full new trade and security relationship, which could take several years. So the UK could be out of the EU by 2019, even though the full shape of its final relationship with the EU might not be clear until the mid-2020s.

If a second independence referendum doesn’t take place until around 2022, then – if Scotland voted Yes – the path back into the EU as an independent member state could be slow and cumbersome. Formal talks to join the EU, if Scotland left the UK say in 2024, could take two years or more. With two to three years to ratify the accession treaty, Scotland might at best re-join the EU by 2028 or 2029.

So Scotland could be outside the EU for a decade. Those wanting an independent Scotland in the EU must choose: either a rapid second referendum, staying in the EU when the rest of the UK leaves in 2019 – perhaps with a transitional status until its new member state status is ratified – or being caught up in the detailed politics and economics of Brexit for several years, then enmeshed in a slower, less certain EU accession process until almost 2030.

Surely Scotland, with all the good will, could be fast-tracked back into the EU? Perhaps, but if Scotland spends half a decade outside the EU before asking to re-join, both the EU and Scotland will have moved on.

Meanwhile, Scotland will not be protected from the negative impacts on the UK of Brexit, including foreign direct investment going elsewhere in the EU and lower growth.

If, post-Brexit in 2019, the UK is no longer in the single market, EU regulations will be unwound and replaced by new laws, a detailed, time-consuming process for politicians and all those affected by the new laws.

Scotland, post-Brexit, could choose whether to keep some of its laws in line with EU ones, from agriculture and fish to the environment. But if Scotland goes down a different path to the EU on a range of laws, it will already be making a choice.

And many EU laws and trade policies will be replaced at Westminster, not Holyrood. The more Scotland’s laws diverge from EU ones, the more time-consuming re-joining the EU becomes.

Scotland is closely intertwined with the EU across economic, social, and political spheres. If that is ruptured, the path to independence, and to re-joining the EU, is a very different one to Scotland staying inside the EU. For now, Scotland is in the European Parliament and part of the single market. It has a presence it will lose after Brexit.

It is much easier to negotiate transition to a full member state if you are already in than out and diverging from the EU.

And whether by the mid-2020s the EU will still be keen on welcoming an independent Scotland is unclear. The EU has already gone cold on enlargement to the western Balkans.

By then, the EU will have moved on – with new policies and strategies, with tackling, for better or worse, its big challenges at present. At the least, getting back into the EU will take much more time – not only from politicians and officials but also from businesses, universities, regions – over several years.

Scotland has to choose. Does it want to stay in the EU in 2019, following Sweden, Ireland and Finland in terms of influence as a new member state, or does it want to spend a decade caught up in the time-consuming, inward-looking politics of Brexit, finally re-joining the EU in 2030?

The choice, and the implications of delay, need to be debated now.

Kirsty Hughes is associate fellow with Friends of Europe in Brussels.