Anyone who rushed to use up as much of their Stock and Shares ISA contribution limit before April rolled round might have regretted their timing soon after.

A few days before the ISA deadline, President Trump announced sweeping tariffs on imports from just about everyone. Within days the FTSE 100 had slumped to 7,545 points. That’s a whopping 15% loss from March’s all-time high.

The index has already regained about half that loss. But we’ve no idea what might happen next. So what can we do to defend our ISAs from possible pain to come?

When it rains

One approach is to try to make the most of share price falls and buy. Look at what happened to Apple (NASDAQ:AAPL) stock…

Tariffs on China, one of Apple’s major suppliers, reached a whopping 145%. It seems the aim was to encourage Apple (and other tech companies) to move production to the US.

CEO Tim Cook already described that as impossible a few years ago, as the country doesn’t have the skills to do it. And in recent days, one analyst reckoned a fully made-in-USA iPhone would have to cost as much as $3,500.

Within days, Apple stock crashed 24%.

Sell, or buy?

Billionaire investor Warren Buffett urges us to buy when others are panicking and selling. There was one key question to ponder. Would the US government allow its most profitable tech companies to fail, or find ways to help?

Almost instantly, semiconductors, phones, and so on were to be exempt from these new tariffs. Or maybe they’ll face different levies instead. Whatever specifically happens, do we really believe this is the end for Apple?

Those who didn’t think so and bought after the immediate crash are already in profit. It takes strong nerves to be able to do that in the face of the huge uncertainty-driven risk that lies ahead. But a good number of investors have already been snapping up fallen Nasdaq shares, some of which are on pretty low valuations.

Do nothing

One alternative is to take no short-term action at all. I’d wager that’s what most of the UK’s ISA millionaires are doing. Not because they have so much money, but because they were already prepared for the ups and downs they knew were near certainties.

The key is to diversify, and that’s why I like investment trusts so much. It’s something I have in common with the millionaires. I’m still working on the million.

Spread the risk

City of London Investment Trust is my top pick. It spreads money across a range of mature UK shares to provide good income. It’s still exposed to stock market crash risk. And it fell 16% in a few days. But it’s already recovered almost all of that.

There’s added risk that if its 58-year streak of annual dividend rises should falter, the price could slump. But that’s the kind of risk level I can live with.

Oh, and a smaller dabble in Scottish Mortgage Investment Trust also gives me some exposure to Nasdaq tech stocks. Maybe I should buy some more.