For many years, observers of the US-Mexican border have pointed to ``push-pull factors'' to explain the northern migration of Mexicans to the United States: Mexicans pushed from their country by poor economic opportunity -- pulled to the US by the availability of work. In the future these terms -- push and pull -- should continue to apply to the way the two nations relate to each other.
Pushing the two countries together will be the continued rapid growth of the border region, with its resulting environmental and infra-structural problems. Urbanization will be especially fast in Mexico. Population gains for Mexico's northern border are the highest in the country, surpassing even Mexico City.
Also pushing the countries together will be policy shifts in both nations allowing more official communication and decisionmaking at the local and state levels.
But some border-region observers also foresee a number of factors tending to pull the two sides apart. One is a falling peso, which could force Mexicans along the border to look away from the north and more to the interior of their own country. In addition, Mexican mistrust of US motives and perceptions of American arrogance vis-`a-vis the border region could continue to pull the two sides away from each other.
Lino Vega exemplifies the cooperation that has brought the two sides of the border closer together. As plant superintendent of the Nogales International Wastewater Treatment Plant, Mr. Vega oversees treatment of sewage from both Nogales, Ariz., and Nogales, Sonora -- two cities separated only by the international border.
``Considering the terrain, a combined plant is really the most logical solution,'' says Vega, noting that at Nogales, the flow of water is into Arizona, where the plant is located.
Payment for water treatment is determined by the two countries' International Boundary and Water Commission (IBWC), according to the volume of water treated from each side, and respective treatment standards. Thus Mexico does not pay for chlorination of the effluent, since that is not the practice south of the border.
Yet a solution that appears logical to Mr. Vega is unlikely to be repeated along the border. The trend for at least a decade has been for each side to treat its own sewage -- a solution that has not always meant quick remedy of border water pollution problems.
In San Diego, which has been plagued for years by sewage spills from Tijuana, plans to treat the southern city's wastewater in the US were terminated when Mexican authorities opted to build their own treatment plants.
``That was a political decision by Mexico,'' reflecting a desire to maintain sovereignty over its own affairs, says Manuel Ibarra, secretary of the US section of the IBWC. Yet other border specialists say the decision reflects Mexico's distrust of US actions along the border.
The slowing of border crossings to a snail's pace this summer after drug-related violence in Mexico against US government agents is a case in point. Such a step ``shows the Mexicans what we're capable of doing,'' says Joseph Nalven, associate director of the Institute for Regional Studies of the Californias at San Diego State University. The Mexican concern, Mr. Nalven says, is that if joint water or sewage-treatment projects were developed, ``What's to stop [the Americans] from some day shutting off th e pipes?''
Just the lack of common priorities is cause enough for friction between the two sides of the border. Said Julio Torrescoto Mazier, Tijuana's assistant director for planning, in a recent San Diego speech, ``While you may be worried about pollution on your beaches, we are concerned about having enough water to go around in our community.'' Noting that 50 percent of Tijuanans don't have running water, he added, ``If we have to choose between a sewage line and a water line, we'll choose the water line. The pollution of Imperial Beach will not be our priority.''
In spite of these differences, Mr. Torrescoto is one border-region official who speaks optimistically of policy shifts on both sides that should enhance local control and communication.
In 1983, a highly centralized Mexico began allowing states and municipalities more autonomy in setting priorities and responding to their own specific needs. That trend, Torrescoto says, promises perhaps no immediate ``binational planning along the border, but at least to facilitate the flow of communication and information.''
At the same time, implementation of President Reagan's New Federalism -- that is to say, decreases in federal assistance to states and municipalities -- is also leading to a greater emphasis on local solutions on the American side.
In 1982, California established the Office of California-Mexico Affairs, and the state Legislature has begun holding hearings on issues affecting the two sides of the border. In Texas, state agriculture officials signed an agreement with Mexico this summer to promote joint research, reduce trade barriers, and aid farmers on both sides of the border by matching growers with markets.
``Most of us along the border agree we can solve our own problems better without interference from either federal government,'' says Howard Applegate, a civil engineering professor at the University of Texas at El Paso who specializes in border pollution. Noting that the IBWC has been reluctant to add air quality to its charge, Dr. Applegate says local governments should take advantage of their increased autonomy to address joint pollution problems.
Along those lines, some border experts advocate extending the concept of local autonomy to create a special zone of regional government along the border.
Ellwyn Stoddard, an anthropology and sociology professor at the University of Texas at El Paso, proposes a 200-mile zone along the border in which local authorities could make regional agreements. ``In everything from health care to local pollution and planning,'' says Dr. Stoddard, ``we who know best about the special circumstances we face down here would be able to address our own problems.''
Stoddard says his proposal differs from that of a border trade zone, recently proposed in Congress, because it would go farther in addressing the border's problems by ``removing bureaucracy, not adding to it. A free-trade zone would mean three borders instead of the one problem we already have.''
Economically, a falling peso is likely to continue its profound effect on border relations. Now at about 500 pesos to the dollar, some experts do not rule out a tumble to 1,000 pesos to the dollar by the turn of the century.
Currently as much as 40 percent of a Mexican border family's income is spent in the US. The fallout from any abrupt drop in Mexican spending across the border, as occurred after a major devaluation of the peso in 1982, is mixed: hardly felt in big and diversified San Diego County, but crippling in more isolated border towns farther east.
Some experts predict the peso's continuing decline will force border Mexicans to reorient themselves away from the US, and toward the interior of their own country.
Gustavo del Castillo, a research fellow at the Institute of the Americas in La Jolla, Calif., notes that California-Mexico trade fell about 60 percent, from more than $3 billion to $1.5 billion, after the 1982 peso devaulation.
Another research fellow at the institute, David Barken, says the Mexican border region's growing ``inward orientation'' will be positive, because it will force Mexicans to produce goods, especially food, for domestic rather than foreign consumption.
``At this point in history you can't close off the world,'' says Mr. Barkin, who is also director of an economic development institute in Mexico City. But reduced reliance on American products, he says, will necessarily entail the kind of economic development the Mexican border region needs.
Yet even if a declining peso forces Mexican consumers to spend more at home, it will also make Mexico an even better bargain for American tourists and businesses seeking cheap labor. And this will only increase the country's dependence on its northern neighbor.
In any case, most border observers see the penetration of both sides by its neighbor as continuing in spite of fluctuating economic conditions.
``The [Mexican] border states are highly influenced by their proximity to America,'' says Guillermina Valdez Villalva, a social psychologist in Cuidad Ju'arez with the Center for Northern Border Studies. ``Much of the country has been suspicious of . . . [northern Mexico's] orientation,'' but she says that perception is changing.
``Before the North was the black sheep. Now it's seen more as the training ground for what may be the future of Mexico as a modern industrial state.''
And from the US side, IBWC secretary Ibarra says he's confident the border's ``cooperative mechanism'' will continue to be strengthened. ``It may not be perfect, but at least we see the communication increasing. For a border region that could almost double in population to 14 or 15 million people by the year 2000, that's important.''
Last of a series. Other articles ran Dec. 9-12.