IF HE ACHIEVES nothing else by his televised announcement of a new plan to preserve the wilderness, Interior Secretary James Watt will probably succeed in leaving the impression in many people's minds that he is a protector of wild lands and wildlife--or at least that he's not half as bad as he's been painted. Considering the facts, that's quite an accomplishment.

"The wilderness should be preserved," said Mr. Watt last Sunday, "and that's why the president and I will be asking Congress to preserve it." Never mind that Congress took care of that 18 years ago with the passage of the Wilderness Act, and that no one perceived the need for additional protections through four Republican and Democratic administrations until Mr. Watt took office.

Having created a brand new problem by letting it be known that he would welcome mineral lease applications in wilderness areas and did not think wilderness status was a reason for not approving a mining permit, Mr. Watt proposed a remedy. It turns out, now that the details are available, to be the kind of medicine that treats the disease by killing the patient.

There is a moratorium on new permits to mine in the wilderness in effect until June 1982. The Wilderness Act prohibits mining applications after the end of 1983. Mr. Watt proposed a plan that would prohibit mining and other forms of development immediately, but would effectively end all wilderness protection in the year 2000. The trade- off boils down to 18 months of protection from Mr. Watt's own policies for the indefinite protection provided under current law.

The Watt plan also ends protections for land being considered for inclusion in the wilderness system, and transfers the decision on their suitablility for wilderness from Congress to the president. Even lands already in the system could be unilaterally released for development by a presidential finding of an undefined "urgent national need."

Mr. Watt is not the first to have garnered frontpage headlines and praise from opponents with a Sunday interview show announcement of something that turns out to be different from what it had seemed. But as students of the Watt style know, he is a master of the bold stoke. The new plan is not a change in his policy, which remains "to open the wilderness." For future reference, we conclude with his own description of his approach to policy-making: "Compromise is not in my vocabulary."