Table 1.
On-farm maize richness (farm-level averages) across Mexico, 2002–2007
| Region | Altitude | Varieties/farm | Χ2 for difference of means | |
| 2002 | 2007 | |||
| Mexico | 1.43 | 1.22 | 29.34 (P < 0.001) | |
| High | 1.66 | 1.40 | 9.64 (P < 0.01) | |
| Mid | 1.28 | 1.12 | 6.21 (P = 0.01) | |
| Low | 1.32 | 1.12 | 22.68 (P < 0.001) | |
| Southeast | 1.53 | 1.39 | 4.15 (P = 0.04) | |
| High | 2.21 | 2.07 | 0.40 (P = 0.53) | |
| Mid | 1.26 | 1.33 | 0.22 (P = 0.64) | |
| Low | 1.38 | 1.16 | 14.91 (P < 0.001) | |
| Center | 1.46 | 1.20 | 16.75 (P < 0.001) | |
| High | 1.56 | 1.30 | 6.95 (P < 0.01) | |
| Mid | 1.45 | 1.06 | 7.47 (P < 0.01) | |
| Low | 1.28 | 1.08 | 5.90 (P = 0.02) | |
| West-central | 1.33 | 1.07 | 12.00 (P < 0.001) | |
| High | 1.38 | 1.05 | 11.14 (P = 0.001) | |
| Mid | 1.30 | 1.12 | 1.90 (P = 0.17) | |
| Low | 1.27 | 1.00 | 1.09 (P = 0.30) | |
| Northwest | 1.05 | 1.03 | 0.05 (P = 0.82) | |
| Northeast | 1.08 | 1.04 | 0.42 (P = 0.52) | |
Average number of varieties per farm includes improved, creolized, and farmer varieties. In 2002, richness was highest in Mexico’s southeast highlands, renowned bulwarks of maize diversity. In general, farm-level richness was lower moving northward and toward lower elevations. By 2007, farmers continued sowing more varieties in high than mid or low elevations, but richness decreased in most areas.