UBS says 4 areas will dominate the market throughout the 2020s as big tech's blockbuster decade comes to an end. Here's how to invest in each.

• Tech giants like Apple and Microsoft were kings of the stock market this decade.
• Now Mark Haefele - chief investment officer for UBS Global Wealth Management - is naming fields that could outperform in the 2020s the way big tech has in the 2010s.
• Haefele says stocks are his firm's top bet in coming years, even though they're on track for smaller gains over the next decade.
• But he's hardly bearish on tech, and says investments in 5G wireless technology, artificial intelligence, and big data are also likely to outperform.
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Big tech conquered the world in the 2010s, and the FAANG stocks and their peers might be sorry to see the decade end.

Mark Haefele - the chief investment officer for UBS Global Wealth Management - says a period of smaller stock gains is coming. And he's urging investors to incorporate new and more targeted ideas if they want to stay ahead in the 2020s.

"Although returns are likely to be lower in the 2020s than the 2010s, we believe stocks are still likely to outperform other publicly listed asset classes," he said. "Large-cap technology stocks probably won't repeat their performance of the last decade, but other parts of the market do have the potential to deliver above-average growth."

Haefele says these four trends have the potential to stand out the way tech did in the years ahead.

(1) Sustainability

Haefele says the growing attention to climate change and ways to mitigate or reverse it will result in opportunities to invest in new companies, new products, and green bonds. He points specifically to the growing talk from European leaders about investments in green technology.

"Consumers, governments, and regulators are all going to be big drivers of a shift toward sustainable investments and products over the next decade, and we think that investors who get ahead of that trend will be rewarded," he wrote.

One way to invest in sustainable companies is the iShares MSCI ACWI Low Carbon Target ETF.

(2) Genetic therapies

There's been tremendous innovation in medications that treat diseases on a genetic level, and Haefele thinks that, too, is just getting started.

"We are now seeing a whole new generation of gene and cell therapies gaining regulatory approval to treat certain rare diseases and cancers," he said. "Large-cap pharma is sitting up and taking note, and we therefore expect to see heightened deal activity in the next decade."

He adds that diversification is particularly important in this field because of the high rate of failure for early-stage drug developers. Two ETFs that include several of those companies are the ARK Genomic Revolution ETF and the Invesco Dynamic Biotech and Genome ETF.

(3) Digital transformation

Haefele hardly thinks tech's time in the sun is over, and picks a series of industries that are likely to advance and attract more investment in the years ahead. For example, he says 5G wireless revenue will nearly double in 2020, a springboard to even more growth afterward.

"The combination of 5G, artificial intelligence (AI), big data, and cloud computing will define a new era of digital transformation and innovation in the decade ahead," he said. "We advise diversified investing focused on six key themes: digital data, enabling technologies, E-commerce, fintech, healthtech, and security and safety."

Investors can gain exposure to some of those themes through the Global X Fintech ETF, Amplify Online Retail ETF, and the First Trust Nasdaq Cybersecurity ETF.

(4) Water

The global population continues to grow, and that means demand for water will continue to climb. Haefele says the two most populous countries in the world, China and India, need far more fresh water than they have. He also notes that European countries are creating new water safety regulations that will encourage new investments.

"The world faces a mismatch between water demand and supply, which will be exacerbated in the decade ahead by the effects of demographics and climate change," he said. "Owing to the urgency and scale of water-related issues, and the need for capital spending in emerging markets, we expect continuous revenue and profit growth for the entire water value chain."

One way to get exposure to that issue is through the Invesco Global Water ETF.