WASHINGTON (Mar 8, 1997 00:55 a.m. EST) -- If only more people were vegetarians! That's a key point in two new studies that show the growing difficulty of feeding a world that's adding more meat and milk to its diet.

A more diverse diet places additional demands on agriculture, say the studies released Thursday by the Population Reference Bureau and the Worldwatch Institute -- two Washington-based research groups.

"In fact, if everyone adopted a vegetarian diet and no food were wasted, current (food) production would theoretically feed 10 billion people, more than the projected population for the year 2050," says the PRB report.

But, with rising affluence in some countries -- especially in Asia, more people are hungering to add meat to their potatoes.

China, with 1.2 billion people and an economy that has posted double-digit growth rates for four of the last five years, is leading the pack.

The Chinese are eating more pork, poultry, eggs and beef -- all of which require grain. They're also drinking a lot more beer. Though China already has 800 breweries, its beer consumption is rising at 7 percent a year. It uses most of its imported barley for beer.

"Since 1990, most of the growth in grain use in China has been for feed to fuel the unprecedented growth in its livestock and poultry industry," writes Lester Brown, president of the Worldwatch Institute in his report on food security.

Other parts of Asia are also seeing strong economic growth that's enabling people to move up the food chain. Beef imports are rising in Taiwan, South Korea, the Philippines and Indonesia, while broiler production in India is expanding at 15 percent annually.

Not surprisingly, says Brown, grain stocks are being depleted at an alarming rate. Despite a record harvest last year, carryover stocks fell to 246 million tons -- or 51 days of world consumption, the lowest level on record.

"If you can't rebuild grain stocks, even with a record harvest, when can you?" asks Brown.

He notes the situation is particularly alarming, because the world depends on a single supplier -- the United States -- for half of all grain exports. And, he says it's not uncommon for bad weather to lower the U.S. grain harvest by one-fifth.

"With such climate instability in the country that supplies grain to more than 100 important countries," he warns, "the world is living dangerously."

Brown sees further danger ahead. He notes the world's population, now 5.8 billion, is growing by about 80 million people annually. Also, the world's economy is growing quickly, creating pockets of affluent and demanding consumers.

Yet agricultural production, he says, will have trouble keeping pace. He notes that cropland is becoming scarcer, as rural areas get developed for industrial and residential use.

Every year in Asia, Brown says tens of thousands of new factories are being built, with each one requiring a warehouse and access road that consumes land -- often crop land.

Another dire problem is water scarcity. The reports say aquifers are being depleted in major food-producing regions, including the southern Great Plains of the United States, the Punjab of India and much of central and northern China.

The resulting shrinkage in irrigated areas -- some 14 percent in Texas alone since 1980 -- is slowing growth in the grain harvest. Some arid regions in the southwestern United States have limited farmers access to water.

In China, Brown says farmers in the agricultural regions surrounding Beijing were barred from reservoirs in the spring of 1994. Beijing kept the water for its own soaring needs.

By 2020, the PRB report says, 35 countries are expected to be classified as "water-scarce" -- up from 20 in the mid-1990s.

The report mentions other worrisome developments. It cites an estimate by the U.S. Soil Conservation Service that almost half of U.S. arable land is excessively eroded.

It also sees problems threatening two common solutions. Fertilizer use, which can greatly increase the food supply, will be challenged on environmental grounds, and new agricultural technology will have to fight harder for funding.

"There are warning signs that we may be reaching the limits of agricultural expansion," the report concludes.

Just as daunting, it says, is the problem of food distribution. The report says many low-income countries do not grow enough food to feed their residents and cannot import enough food to close the gap.