Using camera traps, a dab of Calvin Klein’s Obsession perfume and other chemical essences that smell of fermented fruit, eggs and hormones, biologist Sergio Pérez Contreras set about researching the wildlife that lives in the Sierra Juárez. His findings are good news for biodiversity and nature lovers.
In the Zapotec community of Ixtlán de Juárez, timber logging is carried out as part of an effort to strike a balance between social and environmental well-being. However, forest management all over the world produces major changes in ecosystems and their composition and structure.
Is it possible to engage in productive activities without affecting the behavior and distribution of species?
Sergio Pérez prepared to explore this topic in his undergraduate thesis on biology.
Sergio is originally from Ixtlán and, as he explained in an interview, he realized that his community had never been studied in this regard despite its long tradition of forest management. He realized that very little information had been published on the behavior and movement of fauna and flora species as a result of logging in the Sierra Juárez.
The forests of Ixtlán de Juárez in the northern Sierra of Oaxaca have been exploited for over seven decades: first by a private entrepreneur, then by the Tuxtepec (FAPATUX) Paper Factory and lastly by the real owners of forest resources, the indigenous peoples of the region.
The Sierra Norte, also known as Sierra Juárez, is considered one of the most important regions biodiversity-wise, because it is home to the country’s largest number of endemic species and eight of the nine types of terrestrial vegetation: tropical rain forest, semi-deciduous tropical forest, cloud forest, oak, pine, tropical deciduous and thorny forest and subalpine meadow, according to a document drawn up by Conabio’s Sustainable Productive Systems and Biodiversity (SPSB) project.
Sergio found that although forest management did not pose a serious threat to the region’s biodiversity, it did have an impact on its behavior and distribution. “Biodiversity continues to exist in these forests because species haven’t been excluded, nor have they moved to other areas, unlike other places where forests are felled without any reforestation or management. In these cases, the fauna completely disappears because the forest’s particular characteristics cease to exist”.
Sergio’s research identified the most striking changes in the logging areas that used the clear-cut forestry method with alternating strips. There, he noticed that certain mammals had benefitted such as the white-tailed deer (Odocoileus virginianus), which feeds on fungus, lichen and ramonea, the foliage and tender branches of bushes, whereas others, such as the margay, were adversely affected.
The clear-cutting technique involves the partial, temporary harvesting of the pine-oak forest. The logging company removes all the trees from a strip approximately 50 meters wide and 600 meters long, leaving about 400 meters of preserved forest between the strips that have been removed. From the air, it resembles a mass of untouched forest, interspersed with clearings without vegetation or with budding vegetation. Before the rainy season, the pines produced in the community nursery are therefore transplanted and as they grow, they are supervised and assisted by the local forestry service.
For his research, Sergio Pérez set up 15 camera traps with motion sensors in three forest areas assigned for various activities, with their corresponding gradient of human presence. Five cameras were placed in a conservation area where there was virtually no human presence; another five in an area of forest rehabilitation where there was a group of foresters fighting the bark beetle plague, and the last five in a logging area with a great deal of activity and human disturbance.
He found that in general, logging areas had greater species diversity, a finding that tallies with other related research.
Thus, several animal species in the region have benefitted from the use of clear cutting. A case in point is the white-tailed deer, a herbivore present in much of North America, Central America and part of South America. Its extensive territorial distribution means that it is found in a variety of ecosystems, although it prefers wooded areas that are not densely tree-covered for shelter. In his research, Sergio recorded four times as many deer in the extraction strips as in the conservation area. Sixty-four per cent of this species were detected in the clear-cut strips, while only 17% were registered in the conservation area. The question is why?
A clearing in the forest, newly stripped of its tree population, creates microenvironments that promote the growth of soil-forming plants. Many legumes or plants with high amounts of nitrogen and protein grow in soils with low nutrients, and are the food of choice of the white-tailed deer that shifted to this logging area.
Sergio also found that in this area, the adjustment of organic matter, resulting from forest harvesting, created microclimates ideal for the mouse, rabbit, reptile and insect populations that thrive in leaf litter and rotting logs. This phenomenon attracted gray foxes (Urocyon cinereoargenteus) and ring-tailed cats, (Bassariscus astutus), which prey on smaller species.
As the biologist explained in his thesis, these carnivores are highly adaptable to changes in their environment, and sometimes actually benefit from the activities and presence of human groups because of their non-specific habits and enormous ability to find shelter and food.
Obviously not all the species in the Sierra Juárez benefited from the alteration of their habitats, the most striking example being the margay. While Sergio had three sightings of this spotted cat in the conservation area, he saw just one in the logging zone. The biological characteristics of felines make them highly sensitive to the disturbance of their habitats: although some cats adapt, others do not. The margay is the Mexican feline that carries out the largest proportion of its activities in trees. This explains why it has avoided the strips without forest cover.
Sergio’s final reflection: sustainable forestry practices alter the ecosystems where they operate, yet they still have the necessary characteristics for wildlife to inhabit them.