What Caused the Decline of the Mayan Civilization?

     The  collapse  of  the  Mayan civilization at the end of the so-called classic period, between 200 and 900, is  a  persistent  archaeological mystery.  The  classical  Maya  were  the  most advanced   of   the   pre-Columbian civilizations, anchored by a collection of city-states in the lowlands of morden-day Guatemala.  Belize,  and  the  Yucatan Peninsula. But around 700, these city- states began an inexorable decline that ended in their total abandonment. While the independent Maya survived until the Spanish conquest in the late 17th century. the postclassical Maya were a less urban and populous civilization.   Archaeologists have posited a number of theories explaining the decline of the classical Maya, from foreign invasion to disease epidemic to a collapse in trade with neighboring cultures, but one of the oldest and most persistent theories centers on drought. The Yucatan Peninsula and Peten Basin were already pamcularly susceptible to variability in rainfall-the soil is thin and sandy, and a regular seasonal drought complicates  agricultural  productivity.
 
       Though the Maya had solved this problem    through advances in fertiIization and    irrigation, studies of soil and stalagmites in    the region indicate a decline in rainfall of   between 25 and 40 percent in the late    classical period. For a culture living off an   already  fickle  water  supply,  this   megadrought may have been too much for   even  advanced  Mayan  hydrological   engineering to overcome.
   
        Drought by itself, however, doesn't  explain the fall in its entirety. It doesn't  explain why the Maya didn't return to the  classical cities after the climate righted  itself in the second millennium or why the  northern  cities  that  ascended  in  the  aftermath never reached the heights of the  lowland city-states. Nor is it clear why the  drought occurred in the first place. It may have been cyclical, but some researchers believe that the Maya instigated the drought by clear-cutting rain forest, cutting short the water cycle that topped off the reservoirs that slaked their thirst during the dry periods.
  
      Almost as mysterious as the decline of  the Maya is the fact that the classic Mayan civilization took root where it did. Dense, urban settlements dependent on agriculture have not historically thrived in jungle climates rooted in limestone soil. That the Maya flourished there at allis testament to the ingenuity of their civilization.