(Opposite) Maya forester putting a growth band around a tzalam (Lysiloma latisiliquum) tree in the Selva Maya of Quintana Roo, Mexico.
Eight forestry ejidos along the eastern coast of the Yucatán Peninsula in Quintana Roo, Mexico, based in Chetumal (N18°30´13´´, W88°18´19´´), 2005–2007
The Selva Maya extends through Guatemala, Belize, and the Yucatán Peninsula of Mexico. Comprising more than five million hectares, it is the largest contiguous tract of tropical forest in Central America, second only to Amazonia in the Western Hemisphere. Much of the intact forest in Amazonia is conserved in parks, extractive reserves, and other types of protected areas under government control. In contrast, over half of the forests in the Selva Maya are owned by ejidos, communities that collectively control, use, and manage their agricultural and forest lands.
Local communities have been managing forests in the Selva Maya since pre-Columbian times.1 In recent years, community forestry activities in the region have largely focused on the production of timber—in particular, export-quality mahogany (Swietenia macrophylla).2 The forestry operations of several ejidos in the region have been certified by the Forest Stewardship Council (FSC) to be sustainable, and some have been able to maintain their certification for more than twenty years. These are some of the oldest certified tropical forests in the world.
Many ejidos in the Selva Maya are facing a critical period in the conservation and management of their forests. Several are coming to the end of the rotation period (the length of time between establishment and harvest; it usually includes a series of intermediate cutting cycles) and require new management plans, and others have been given a detailed list of deficiencies that must be corrected before their certification is renewed. In each case, the stumbling block is lack of basic information about tree growth. These data are not expensive or difficult for villagers to collect, but most rural farmers do not know how to make a dendrometer band or conduct a growth study. The growth estimates used in the management plans of many ejidos, for example, are based on government research conducted in other parts of the country, which may not be representative. If the growth estimates are too high, the allowable cuts calculated in the management plan will also be too high, and more wood will be harvested than the forest can sustain. If the growth estimates are too low, valuable timber that could be harvested sustainably will be left in the forest. The best management plans are those based on growth data collected from trees in the forests being managed.
I started working with a group of eight forestry ejidos in 2005 to initiate growth studies on local timber species. In addition to mahogany, the ejidos monitored the growth of twenty important tree species; almost three thousand trees were fitted with dendrometer bands. This might have been the largest community-based study of tree growth ever initiated in the tropics.
We held three workshops in Quintana Roo to train ejido foresters to conduct a growth study. The format of all three workshops consisted of a morning classroom session focused on the basic principles and methodologies of measuring tree growth, followed by an afternoon session in the field to make dendrometer bands and teach the villagers how to use the other instruments required for data collection, such as a vernier caliper to measure the growth increment recorded by the dendrometer band; a 10-factor basal area prism to count the number of neighboring individuals (competitors) in the vicinity of each sample tree; and a spherical densiometer to quantify the percentage of canopy cover. Each ejido drew up a list of the important timber species that grew in the community’s forests, and drafted an agreement with the project to formalize its commitment to band and monitor the growth of a certain number of sample trees.
Participants in the three workshops responded similarly to the basic forestry concepts and tools we introduced. Foresters have for many years measured tree growth with a diameter tape (d-tape): a steel or cloth tape that expresses the measurement of the circumference of a tree in terms of diameter by dividing it by pi. The diameter of a sample tree is measured with the tape, a specified length of time is allowed to pass, and tree is measured again. The difference between the two measurements is assumed to represent growth. The inherent problem with this method is that many tropical trees grow extremely slowly, and measuring tree diameter with a d-tape is subject to many sources of error depending on where the tape was positioned around the trunk, how tightly it was pulled, whether the bark was cleaned before the measurement, and whether the tape was read correctly. All these vary depending on the person making the measurement. To demonstrate the difficulties, during the morning sessions we would select a sample tree and ask each person to measure its diameter with a d-tape and write the result on a piece of paper—but not tell anyone what it was. As expected, the results differed significantly, in some cases by as much as one or two centimeters. If the annual diameter increment of a timber species is only half a centimeter per year, the d-tape method is not going to provide useful information. Given the amount of grimacing and animated conversation, usually in the Mayan language, that invariably occurred when we compared the diameter measurements from the sample tree, all the workshop participants were convinced that a better way of measuring tree growth was needed.
A similar degree of fascination and enthusiasm was displayed when we showed them how to make dendrometer bands. Each ejido team was given a plastic lunchbox containing several rolls of stainless-steel strapping, several dozen springs, a pair of scissors, a permanent marker, and a vernier caliper, and was promised that more material would be on its way after we had had a chance to review their species lists. In each of the workshops, for every team from every ejido, once we showed them how to make a dendrometer band, it was impossible to get the lunchbox back. The dendrometer band is a simple, yet elegant tool, the utility of which everyone immediately appreciated.
Some ejidos contracted to band more trees than other communities did, but all the communities agreed to start collecting data on the growth of the timber trees in their forests. Even the smallest ejidos committed to band at least three or four hundred trees.
There is a machine shop in Connecticut that makes stainless-steel springs. Shortly after returning from Quintana Roo, I called the store, told the clerk that I was from the botanical garden, and ordered ten thousand springs. There was a long pause on the other end of the phone. “Uh, what are you going to do with all these springs?” he asked. I replied that I was working with a group of Maya foresters in Mexico and that we were going to use the springs to make dendrometer bands to measure the growth of their mahogany trees. I explained that we planned to leave the springs out in the forest, which is why we needed stainless steel. Another long pause while he processed this information. Then, “I think we can give you a little discount on these.”
Their return to their growth bands after one year represented a seminal moment for most of the ejido foresters. Although they had invested the time and energy to locate the sample trees and make the bands, there was clearly a nagging doubt in many people’s minds as to whether the bands would actually work. I appreciate now that a lot of the work is done on faith—from both sides—during the early phases of community collaborations. The ejidos’ doubt was put to rest after they remeasured the first sample tree. The band affixed around this individual, a large mahogany tree, had indeed expanded, and the caliper reading, taken several times, revealed that the tree had grown exactly 0.85 centimeters in diameter over the past year. There was a murmur of approval by everyone in the field crew. The next tree, another mahogany of similar diameter, provided additional insights into the growth of these trees. Caliper measurements, also taken several times, showed that this tree had grown only 0.18 centimeters in diameter. Given that the faster a tree grows, the more wood volume it produces, and the more money it makes for the ejido, everyone was curious about why one mahogany tree had grown more than four times faster than another during the same time period. A frenzy of chatter arose as the crew started assessing the canopy cover, the soil conditions, and the number of competitors around each sample tree. This is exactly what professional foresters do.
I went to the forest numerous times with the field crews to look at their sample trees, read the bands, and record growth data. I was impressed by how deep into the forest they had gone to set up their growth studies, and by the long distances between different clumps of sample trees. Most of the crews had GPS devices, but they did not use them to relocate their growth trees. They just knew where they were. I would follow the crews through the forest, walking for ten or fifteen minutes along an invisible—at least to my eyes—trail, and we would suddenly come on a group of trees with shiny bands and springs. We would read the bands, and then set off walking for another ten or fifteen minutes along another invisible trail to find the next group of trees.
In one ejido, the growth trees were located so far inside the forest that we elected to go by a three-wheeled, balloon-tired motorcycle. I asked, several times, in advance whether there would be room for me on the vehicle, and was assured that there was, that it would be “no problem”—they did this all the time. Four of us ended up piling on the utility trike. I climbed on last, and noticed a little sign (in English) on one of the back fenders—the one that I would be sitting on—warning in bold letters that the maximum capacity of the vehicle was one driver and less than ten kilograms of field equipment. We raced along a muddy logging road for about half an hour, skidding and swerving, and I almost fell off several times. We found all the sample trees, read the bands, and, in good spirits, headed back to the village. No problem.
Walk through forests in the Selva Maya and you will pass a lot of little hills. Some of these hills are hard patches of limestone that have resisted erosion while the surrounding area was gradually washed away and flattened. Geological processes alone, however, have not produced all the topography in the forest. The first evidence of this is a prevalence of stones with flat sides. Keep looking, and the stones will appear to be fitted tightly together—even, in a few places, to make steps. The whole hill is covered with soil and trees, but the slope is atypically constant, smooth and steep. Then you will come on a section of the hill where the stones have collapsed, and a small cave or chamber is visible within. If you ask the field crew, they will affirm that the hill is actually a Maya pyramid and add that there are dozens of them scattered throughout the forest.
During the Caste War of Yucatán (1847–1901), the Icaiche Maya formed a walled settlement in the jungles of Quintana Roo called Chichanhá. The war, a revolt by the indigenous Maya (primarily Icaiche and the Ixcanha) against an oppressive local government comprised mostly of Spanish officials, created an independent Maya state, Chan Santa Cruz, and drove all nonnative people from the region. I had never heard of it, but on one of our trips to the forest to check growth bands, we visited the ruins of the settlement with a young archaeologist from Veracruz who told us the story.
Rather than negotiate with the Spanish during the final stages of the war, the Icaiche rebels moved deep into the forest and created the walled city, which included schools, markets, public buildings, a church, and a deep cistern to provide water for the community. Access to the settlement was tightly controlled. Other Maya groups, as well as the Mexican government, made repeated requests for a meeting to investigate the possibilities of a cease-fire, but the Icaiche consistently refused such offers. As a final resort, the Catholic Church offered to send the local bishop to Chichanhá to say mass. The rebel leaders agreed, the bishop came and left, and, within a few months, all of the residents of Chichanhá had contracted a fever and died.
It took us a long time to walk to Chichanhá, and the absence of a clear trail suggested that villagers rarely came to visit. We saw huge chicle trees (Manilkara zapota), heard the occasional screams of howler monkeys (Alouatta pigra),3 and touched the crumbled walls of an indigenous rebellion. Nobody said much as we walked through the ruins. We tossed a couple of rocks into the cistern to see how deep it was, but we never heard them hit the bottom. The Selva Maya had grown back and erased much of the evidence of the once thriving Icaiche settlement. I reflected on the intensive farming and forest exploitation that must have been practiced by the residents of Chichanhá on this same site a hundred years ago, yet I saw little to suggest that any of these management activities had ever occurred. The forest seemed pristine.
At 2:37 a.m. on August 21, 2007, Hurricane Dean, a category 5 storm with winds of up to 265 kilometers per hour, slammed into the Yucatán Peninsula. The center of the storm passed right through the middle of the Selva Maya, destroying over one million hectares of forest and toppling or decapitating a large number of the sample trees we had banded. The six hundred or so bands that were still in place provided invaluable data on the growth response of tropical trees to hurricanes. Such information was certainly worthwhile, but not what we had in mind when we started the research.
All the ejido forests in our growth study were affected by the hurricane, but to different degrees. The forests that were hit the hardest were, for some reason, those with the highest densities of mahogany. These ejidos consistently made the most money from their forestry operations, and they were also the communities that had the necessary equipment and manpower to clean up the mess. The problem was what to do with all the salvage timber. If it was dumped on the market, the price, even for certified mahogany timber, would plummet. The other ejidos, whose forests contained low volumes of mahogany that consistently generated smaller revenues, escaped the gale-force winds. These ejidos never had the highest-value timber, but in the years following the hurricane they did have some timber to sell. In many respects, Hurricane Dean leveled the playing field in the forestry sector of the Selva Maya.
Hurricanes are a relatively common occurrence in Quintana Roo, and what invariably happens during the dry season in the months following one is that all the fallen trees and slash in the forest catch on fire. Even communities that proactively do salvage cuts and clear the slash from the understory run this risk. All it takes is one neighboring ejido that cannot afford to clean up its forest. In an attempt to avoid this scenario, representatives from several forestry ejidos in the Selva Maya went to Mexico City following Hurricane Dean and petitioned the government for emergency funds to help with the cleanup. The situation became complicated, all the work had to be put out for bids, the funds were delayed, and while all of this was going on, the forests caught on fire in Quintana Roo. We lost a significant number of growth bands in these fires.
In spite of disruptions by hurricanes and wildfires, my collaboration with ejidos in the Selva Maya produced several results of value. Local foresters now have a tool to precisely measure the growth of their timber trees, as well as a deeper understanding of the myriad environmental factors that influence tree growth and yield. The forest management plans produced by the ejidos are also more reliable—and sustainable—because the growth rates used to calculate the annual allowable cut were collected from sample trees in their harvest areas. All the communities involved in the growth study have greatly improved their chances of obtaining or renewing forest certification. The result, however, that made the strongest impression on me was that local communities, with little encouragement, quickly grasped the importance of measuring tree growth and were motivated to band and monitor the annual diameter increment of thousands of timber trees. Few forestry operations in the tropics invest the time and money to measure tree growth; fewer still incorporate these data into management plans. The ejidos, with the help of modern science, are doing both.