Tuesday, December 21, 2010

Let's Save Our Water Supply -- The Forest of Water

By area, Morelos is the second smallest state in Mexico (after Tlaxcala); so small that on a clear day, from the Mexico-Cuernavaca expressway, you see about 80% of the state.  To the east, on the border with Puebla, the highest point in Morelos is the peak of Popocatepetl (17,980').  To the south the Sierra Madre del Sur is the border with Guerrero, to the west the State of Mexico, and to the north the Federal District.  Though you can drive through Morelos, from north to south, in an hour, it contains an amazing ecological and geological diversity.  

Traversing this tiny state are three parallel mountain ranges running east to west, each providing important resources. The ridge you cross on the highway from Mexico City is the Neovolcanic Axis.  Imagine a string of 8,000 volcanos all lined up!  It starts in Colima and cuts right through central Mexico exiting out on the other coast at about the latitude of the port of Veracruz.  Every flat-topped mountain and every pointed mountain in the ridge is a volcano.  

The limestone ridge, since prehispanic times, has been an important source of construction material; both as building blocks and limestone cement. It is one of the principal ingredients in today's Portland cement. Xochicalco, the Cacahuamilpa Caves, and the giant cement factory visible from the highway are located in the limestone ridge. An unusual use of limestone is as an ingredient in tortillas.  In order to grind the corn to make the dough to pat into the shape of a tortilla, the corn first has to be soaked in water and limestone and subjected to heat for 24 hours. 

The Sierra Madre, to the south, is a source of a variety of mineral wealth; Taxco’s famous silver mines are located just beyond Morelos in Guerrero. But many other minerals are also found in these rich mountains.
Many of you will make the trip over the ridge to Cuernavaca during the holidays.  It is one of the world's more beautiful drives.  Since we're in the tropics, where climate is determined more by elevation above sea level than latitude, the quick change in elevation we experience takes us through several ecoregions.  In all of Mexico there are nine great ecoregions of terrestrial vegetation, Morelos harbors seven of the nine (missing are mangroves and rain forests). The drive over the mountain from Cuernavaca into Mexico City takes us through most of them.  

Leaving Cuernavaca, passing the state university campus, we get into a pine forest; desert vegetation is in the area of the switchback named La Pera; followed by an oak forest, characteristic of a much colder climate, left over from the last glaciation; back into a pine forest near Coajumulco; and then Zacaton grasses as the highway takes us through a 9,300' pass over the continental divide and into the Federal District.  As you go through the pass look higher on the ridge, into fir forests.  

As you're making your way up the mountain also notice the dark and porous volcanic rock, most easily seen in the cuts made for highway construction. The porous nature of the rock makes the ridge a natural reservoir.  An average of six feet of water fall per year in central Mexico.  Each drop of rainwater that falls on the volcanic ridge immediately, and instinctively, wants to race down the mountainside, join a raging river, and feel fulfilled by reaching the Ocean.  But when it runs into a blade of grass, a bush, or tree, it comes to a standstill and gets absorbed by the ridge, acting like a giant sponge.  It percolates down inside the mountain and with time, years perhaps, joins an underground river and will finally emerge at one of the many springs located along the base of the ridge.  Thirty percent of the population of Mexico lives on either side of the Volcanic Axis; not because they want to live dangerously, but because that's where the water is. The key to this marvelous reservoir is the forest.  It is for this reason that, even though water is not visible, it is known world-wide as the Great Forest of Water.  Water flows from its abundant springs into Morelos, the State of Mexico, and Mexico City year ‘round, regardless of whether it is rainy season or dry.  If the forest is destroyed there indeed will be a raging river during the rainy season but there will be less and less water flowing from the springs.  The current autopista crosses through the Great Forest of Water and has already affected the amount of water stored in the mountain.  Environmentalists are deeply concerned about the impact on water supply of proposed plans to build another highway along the top of the ridge, connecting Lerma to the autopista and bypassing Mexico City. 

It is hard to quantify the value of a forest, but number crunchers can easily calculate the cost of transporting water from distant sources, and compare it to the cost of the fresh, clean, and free water delivered in abundance year 'round by the Forest of Water right to the doorstep of the Federal District. If you are interested in more information on this topic send me an email and I'll forward two very interesting articles about this environmental threat.  One from The News itself, and the other from the Journal of Wilderness.

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