Many investors don't rank environmental concerns high on the list of metrics they consider when researching stocks, but it's likely more are coming around to the idea that the tides are changing. How the companies we consider investing in treat the planet is part of a major shift in the way many of us view the definition of solid, long-term management practices.

Of course, it's often difficult to know which companies do a bang-up job on earth-friendly initiatives, but here's one fertile resource: Newsweek recently released its Green Rankings 2012.

Green machines
This is the fourth year Newsweek has crunched data on the 500 biggest U.S. companies in order to ascertain which are the most responsible and sustainable of them all. Using data from Sustainalytics and Trucost, companies are compared on the size of their environmental footprints, corporate management, and transparency, and an advisory panel of sustainability experts helped create the methodology.

The results may be surprising, given the types of companies that immediately pop to mind for green kudos.

IBM (IBM 1.05%) took the No. 1 spot this year, with an overall "Green Score" of 82.9. It's particularly cited for its "Smarter Planet" initiative, which is helping its clients do exactly what investors should hope they would do: measure and reduce their resource consumption, thereby saving money.

Hewlett-Packard (HPQ 1.55%) can be faulted for many issues, including its revolving-door management and corporate governance issues over the years, but it's managed to muster green computations that set it high above the rest, in the No. 2 slot. With a total Green Score of 78.5, it's highlighted for having lowered its emissions by more than half since 2005. It's also been a force to reckon with for suppliers, blocking those that are connected to deforestation and illegal logging practices .

The third-greenest company is Sprint-Nextel (S), with a Green Score of 77.5. It was the first such company to take back old devices for reuse, and it encourages consumers to keep their devices out of landfills by offering credits for returning their old phones. It's also set a goal of recycling nine out of every 10 devices it sells by 2017.

The least green
The survey gives us some major underachievers to look at, too; although many energy companies ranked low, the lowest of the low is also a surprising candidate.

Financial company BlackRock (BLK -0.50%) got the lowest score, with a total Green Score of 21.4. Its lack of environmental disclosure or companywide green policies and programs reflects poorly on the company. Ironically, it does have assets under management coined "responsible investments," but BlackRock discloses no details on those.

The second-lowest company on the Green Rankings is Alpha Natural Resources (NYSE: ANR), the company that bought Massey Energy in 2011. It may or may not be a coincidence that Massey Energy was responsible for the Upper Big Branch disaster in 2010, the worst mining accident in 40 years; Massey's history was also marked by environmental controversies. Alpha Natural's currently poor ranking relates to precious little evidence of disclosure of impact assessments, emissions trends, programs to reduce toxic waste, and so forth, even though it does provide a corporate social responsibility report.

Building blocks for the long term
For those of us who aim for socially responsible investing, environment is just one piece of the puzzle; lists like these don't trump important financial metrics like growth rates, industry standing, and valuation. However, how corporations treat the planet is an important aspect to consider and include in the investment research toolbox.

On a bigger-picture level than our own portfolios, big companies possess the clout to push for some pretty big, amazing changes; Hewlett-Packard's hard line with suppliers could make a huge impact on combating deforestation, for example.

Companies that approach their businesses with an eye toward reducing waste, boosting efficiency, and ensuring a healthy world for future generations have one thing going for them: a very long-term and healthy view. This spirit is probably a more important factor than many may currently realize.

Check back at Fool.com for more of Alyce Lomax's columns on environmental, social, and governance issues.