Posted by: Johan Normark | June 4, 2009

Climate and the “Maya collapse” pt 6: The frequency of droughts

Investigations by the CRAS project have detected a fluctuating settlement pattern in the Cochuah region (Shaw in preparation). Larger sites with a large or a more or less permanent water source (Ichmul, Sacalaca, and Yo’okop) have a far more continuous settlement through time compared to smaller sites without permanent water sources. These smaller sites were largely settled during drier periods, not during wetter periods. A substantial proportion of these small sites have karstic features.

The chronology of the use of karstic features in the Cochuah region below has been established from test pit excavations, dating ceramics through typology, survey and mapping. The dates are accompanied with dates of proposed droughts listed by Bracamonte (1994), Farriss (1984), García-Acosta et al. (2003), Gill (2000) and Mendoza et al. (2007). Maps can be found here.

  • 600-300 B.C. The rejollada (a sinkhole not reaching the water table) at Chakal Ja’as had substantial activity during this period but there is no documented activity at the surface site (Shaw 2005). Dry periods occurred around 480 B.C. and between 370 and 265 B.C. (Gill et al. 2007).
  • 300 B.C.- A.D. 250. Other sites with karstic features in the region were settled at this time. Punta Laguna had low water levels at the end of this period (Hodell et al. 2007). Two peaks of droughts are noted in Chichancanab between A.D. 120 and 190 (Gill et al. 2007).
  • 250-750. The settlement at smaller cave sites and the larger site of Sacalaca were scarce with a possible exception for Xmakabha near Ichmul (Johnstone 2006). Ichmul and Yo’okop had substantial settlement. There is a documented drought at Punta Laguna (535-550) (Hodell et al. 2007). Otherwise, this was a period devoid of known droughts.
  • 750-1100. This was the period of substantial settlement expansion/dispersion to caves. All sites with settlements at caves were occupied. A series of droughts have been proposed for 760, 810-818, 860-862 and 910-915 (Haug et al. 2003). At Chichancanab there is evidence of droughts in two phases, 770-870 and 920-1100 (Hodell et al. 2005).
  • 1100-1544. Some caves were used for rituals and perhaps for pilgrimages. The evidence for settlement near caves is scarce with the possible exception of Gruta de Alux and Huay Max, both cave sites visited this year. Gill (2000) proposes several dry periods for the Postclassic; 1110-1160, 1240, 1330-1360, and 1450-1500.
  • 1544-1847. The Colonial settlement at Sacalaca was located fairly near a cenote. The possible cenote(s) at Ichmul may have been covered by later architecture (Flores and Normark 2005). However, there is no known settlement around the “peripheral” caves during the Colonial period and the early independence. This could reflect the influence of the Church or the early congregación policy. However, the caves themselves appear to have been used. Droughts are known from these dates: 1535-1541, 1551-1552, 1564, 1571, 1575-1576, 1648, 1650-1653, 1661, 1725-1727, 1765-1774, 1800-1805, 1807, 1809-1810, 1813, 1817, 1822-1823, 1834-1835, 1837 and 1842.
  • 1847-1901. The San Pedro Sacalaca and Santa Cruz caves may have been used during the Caste War (Normark 2003; Shaw 2004). Caves became important to the Cruzob religion that emerged in 1850 (Reed 1964). Droughts occurred in 1854, 1881-1882, 1887, 1889 and 1896 (Mendoza et al. 2007).
  • 1901-2008. The main way to date modern cave use is through graffiti. Carvings and paintings with alphabetic writing exist but they are difficult to differentiate from similar texts from the Caste War or the Colonial period. This concerns for example Chakal Ja’as, Huay Max and Yo’aktun. Droughts occurred 1903-1906 according to Gill (2000) and 1923-1924, 1928-1929, 1935-1936, 1962-1963, 1971-1972 and 1986-1987 according to Mendoza and others (2007:163).

The above dates of droughts show somewhat different frequencies of severe droughts. Hodell and others (2007:235) have detected a frequency of 50 years between severe Prehispanic droughts. Haug and others (2003) propose a frequency of 40 to 47 years. These proposed frequencies have been used by Gill (2000), and more recently Gill and others (2007), to propose a collapse in four sequences with fifty year intervals (760, 810, 860 and 910). Gill suggests these sequences are related to volcanic eruptions above a certain magnitude that affect climate patterns (Gill and Keating 2002).

However, Mendoza and others (2007:166), based on historical written documentation, suggest a somewhat longer periodicity of roughly 60-64 years between severe droughts, and notes that there were some time periods during historical times that had no severe droughts (1577-1647, 1662-1724, 1728-1764, 1774-1799 and 1855-1880). Most frequent droughts occurred between 1800 and 1850, just before the outbreak of the Caste War and its initial phase. However, if one look at the table in Mendoza et al. (2007:155) one can see that there are 10 recorded droughts during the earlier 240 years (1535-1774) and 15 droughts during the later 96 years (1800-1896). This suggests a sampling problem since earlier records are fewer than later ones. Either the written records describing droughts are less preserved, or earlier people made fewer notes, or the parameters for droughts have changed among officials through the centuries, or it reflects a real trend of increasing droughts (perhaps related to the emergence of industrialization and its initial effect on global warming). However, the table also shows that droughts are much more common than every 40 to 64 years. Mendoza and others also show that most modern and historical droughts only lasted one year but some could extend for up to ten years. This means that people for sure had both knowledge of and strategies to cope with this very frequent problem.

Of course, as Gill (2000) argues, if the drought was severe enough no knowledge and strategy would be sufficient. There is clearly a decrease in archaeological remains during the later part of the Terminal Classic, even in the Cochuah region. But there are too many flaws and assumptions in the palaeoclimatic models for us to attribute the drying trends seen in nearby Lake Chichancanab as the sole causes for this decrease. Our parameters of what constitutes a drought may be different from the ones used by past officials and farmers. Further, how can we know what amount of rain that actually fell or did not fell in a particular local area from sediment cores? Here Hodell and others (2007) have a more nuanced approach than Gill (2000) and Gill et al. (2007).

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