WORLD TRADE is one of those earnest, boring subjects. The issues range from the ludicrous (canned mushrooms) to the incomprehensible (semiconductors). The following paragraphs concern trade. Why read any further?

There's really only one reason -- that the shifting trade patterns underlie several much more interesting things such as future unemployment rates, recovery from the recession and, consequently, the 1984 presidential election. So read on.

At the end of this month, in Geneva, trade ministers from most of the world's governments will convene to begin revising the rules of international commerce. The organization is called GATT -- the General Agreement on Tariffs and Trade -- and for nearly 40 years it has worked quietly to expand trade by upholding, more or less, an accepted code of conduct. It called the coming meeting to renew the momentum toward wider trade. But, with the deepening recession, the trend to protectionism is rapidly accelerating, and the free-traders have belatedly realized that they are going to have to struggle desperately to keep GATT from backsliding and building more trade barriers.

Boring or not, there is one thing that you can say without qualification about world trade: it has been one of the great engines driving economic growth and raising standards of living since World War II. Total economic output of the industrial countries, taken all together, has doubled over the past 20 years. One crucial reason is that, in those same 20 years, the volume of their exports and imports has risen by 31/2 times -- steadily pushing toward greater national specialization, better use of resources and higher earnings. Sir Roy Denman, who represents the European Common Market here in Washington and has been a major contributor to the process, made that point along with a couple of useful suggestions on the opposite page yesterday.

But trade, in times of high unemployment, is pure torment to politicians. Foreign imports jeopardize domestic jobs. True, they also usually promise more and better jobs in growing export industries. But in a recession, it's the endangered job that draws attention and sympathy. Future jobs in exports always seem very distant and uncertain. New industries, full of self-confidence, look to themselves. But the dying elephants all come trailing lugubriously to Washington.

Perhaps GATT is a little more interesting than it seems at first glance. The ministers at Geneva are going to have to wrestle with a paradox carrying enormous consequences: protecting industries kills economic growth. They are going to have to keep losing some jobs at home to imports if the industrial countries are ever going get their soaring unemployment rates down.