THE FIRST item of legislative business before the Senate when it resumes operations today will be the Alaskan lands bill. The debate is likely to be long, ferocious and misleading. Before it begins, it may be well to recognize that neither of the two competing versions of this legislation is as bad as its opponents advertise.

The Senate energy committee bill, which is being opposed by the Carter administration and environmental organizations, would not open up Alaska's vast spaces to total destruction by exploiters of natural resources. The amendments that will be proposed to this bill -- and that are being opposed by the energy committee and the state of Alaska -- would not destroy Alaska's economy and would not deprive the nation of vast oil supplies.

The lands bill -- in either form -- is not an energy bill, a gun control bill or a "get" Alaska bill, despite all that has been and will be said. It is a bill that will determine how much federal protection the known and unknown resources of that state receive. The energy committee bill tilts toward opening up for use now or in the near future certain areas that the amendments, as well as the legislation that passed the House last winter, would put into the federal deep freeze.

This difference in approach is illustrated by the way the two versions treat the Arctic Wildlife Range. The energy committee wants that range opened now to oil exploration while reserving to Congress the future decision on whether to extract any oil that might be found there. The amendments, and the House bill, would declare the range to be wilderness where such exploration would be barred.

The difference is critical. If the range is closed to exploration, oil will be sought elsewhere in Alaska. If it is found, pressure to open the range will ease. But if the range is opened now, the resources used in exploring it will not be used elsewhere and, if oil is found under it, the pressure to develop the range -- at the expense of its wildlife -- will be enormous. That leads us to support the conclusion of the Carter administration: put the range in wilderness and look elsewhere first.

The Alaskan state government fears that putting a wilderness stamp on this range (and other areas) will close them forever to development. That is a legitimate fear because Congress has no record of releasing lands once they are designated as wildernesses or national parks. But the wilderness designation should not be regarded as totally irreversible. Its purpose is to preserve for the future as much unspoiled acreage as the nation can now afford. What the policy-makers of the future do with it is their business. Surely future members of Congress will not believe themselves unable to open the range (or other areas, such as the forests of southeast Alaska) if the time comes when the resources they contain are needed desperately.

This approach -- save what you can for the future -- is the one that should guide the Senate's work on this legislation. That is particularly true because knowledge of Alaska's resources is still skimpy.The wildlife range may rest on a vast pool of oil, although the odds are against it. There may or may not be vast pools elsewhere. In this situation, the wise policy is to preserve the best of Alaska until -- at least -- the rest of it has been fully developed. The five key amendments to the energy committee bill do just that.