Disputes - international:
abundant rainfall in recent years along much of the Mexico-US border region has ameliorated periodically strained water-sharing arrangements; the US has intensified security measures to monitor and control legal and illegal personnel, transport, and commodities across its border with Mexico; Mexico must deal with thousands of impoverished Guatemalans and other Central Americans who cross the porous border looking for work in Mexico and the United States

Refugees and internally displaced persons:
IDPs: 5,500-10,000 (government's quashing of Zapatista uprising in 1994 in eastern Chiapas Region) (2007)

Illicit drugs:
major drug-producing nation; cultivation of opium poppy in 2007 rose to 6,900 hectares yielding a potential production of 18 metric tons of pure heroin, or 50 metric tons of "black tar" heroin, the dominant form of Mexican heroin in the western United States; marijuana cultivation increased to 8,900 hectares in 2007 and yielded a potential production of 15,800 metric tons; government conducts the largest independent illicit-crop eradication program in the world; continues as the primary transshipment country for US-bound cocaine from South America, with an estimated 90% of annual cocaine movements toward the US stopping in Mexico; major drug syndicates control the majority of drug trafficking throughout the country; producer and distributor of ecstasy; significant money-laundering center; major supplier of heroin and largest foreign supplier of marijuana and methamphetamine to the US market (2007)