When it comes to investing in natural resources, Doug Leonzi advises his clients the way he manages his own investments - he believes they should be in most portfolios, including his.

Leonzi is an advisor at National Penn Bank in Allentown, Pa., with PrimeVest serving as the broker-dealer. He dollar-cost averages into funds, ETFs and specific stocks that focus on this sector to take advantage of opportunities from global expansion.

"The global economies are in a standstill and there's a big fear of a global recession, but as certain global emerging markets grow, they're going to grow their infrastructure," he says.

Most investing experts that focus on infrastructure believe that these needs - from railways to bridges-are so sweeping and these projects so crucial, that advisors have a good opportunity to guide clients with a host of portfolio decisions.

To start, infrastructure in the U.S. needs attention, say advisors and portfolio managers. Faced with a prolonged recession, plus growth into urban areas, many cities and states have not been able to keep up.

One reason, says Forward's Aaron Visse, is that non-discretionary spending in the U.S. - programs such as Social Security, or anything required by law - as a percentage of the budget has been growing. So discretionary spending-from defense to highway construction - as a percentage has been shrinking.

"As a result, there has been an under-investment in areas such as infrastructure and the longer this occurs, the less competitive a society becomes, particularly when other countries, such as China, are ramping up their spending," Visse says by email.

The American Society for Civil Engineers put the U.S.'s five-year infrastructure requirement at $2.2 trillion back in 2009. The European Union requires approximately $2.1 trillion in infrastructure projects, according to the World Bank's Office of the Chief Economist.

In the U.S., some projects have been green lit, like a $2.9 billion expansion of Washington's Metro system. Larger projects include a $70 billion, high-speed rail system in California, expected to start early next year and send trains traveling at about 220 miles-per-hour along California's coast, linking major cities from Sacramento to San Diego.

Outside the U.S., advisors are focused on developing markets that are trying to meet rapid economic growth. One area of interest for Robert Becker is natural gas, particularly in China. In the U.S., demand is running at about 1 percent a year, but it's in the high single digits in China. "They're building out energy systems, both oil and natural gas," says Becker, the senior vice president and lead portfolio manager for Cohen & Steers Global Infrastructure Fund, which has close to $2.6 billion under management.

Overseas firms can sometimes offer cheaper alternatives than their domestic counterparts, says Visse. On the whole, Visse prefers stocks over bonds as he sees equities offering a better risk-reward dynamic. He looks for firms with longer-term growth rates, such as the Germany-based Siemens, China-based energy distributor ENN Energy Holdings, or Perusahaan Gas Negara, a state -owned gas and energy company in Indonesia. But he notes that investors should be thorough in their research to avoid over-leveraged firms.

"I absolutely think if you were shot to earth and told to find cheap equities, you'd find that the safest companies have been bid up, but in other areas is where there are opportunities," says Visse. "Infrastructure offers a good investment."

Russ Cesari, at Northwest Financial, is interested in both core elements and materials - from the iron ore pellets used in the construction of steel to the equipment used in construction. He looks for mutual funds that take these two areas into account.

He also looks at both global and domestic opportunities, believing that today's urban dwellers create plenty of places for investors to realize growth today. "There are good opportunities for these publicly traded companies because the government can't make all these investments," he says. "There's a compelling long-term case for infrastructure."