Análisis jerárquico de la intensidad de cambio de cobertura/uso de suelo y deforestación (2000-2008) en la Reserva de la Biosfera Sierra de Manantlán, México

Abstract

Hierarchical intensity analysis of land cover/use change is a quantitative framework of nested spatial analyses that allows the estimation of changes using a change matrix at three levels of order: time interval, category, and transition. The intention of this article is to present the advantages of this framework in analyzing the dynamics of land use/ cover change using the change matrix, which has been commonly used for this purpose. However, even though the change matrix identifies some key patterns, it does not indicate whether the observed patterns have derived from processes that are systematically more or less intense than a random or uniform process. Among the most important considerations in intensity of change analysis is the use of a hierarchical order that starts at the time interval level, then takes into account the level of categories and culminates at level of transitions. Thus, the areas of each category at the start and end times serve to establish a uniform basis for the comparison between the expected and observed changes. In this way it is possible to define more clearly the patterns of change between time intervals and identifying potential drivers of the process. We present apply this analysis for two time periods (2000-2004 and 2004-2008) in the Biosphere Reserve Sierra de Manantlán (brsm), a highly heterogeneous area in terms of vegetation type and land use, which was declared as a reserve in the last decade of the twentieth century. We used the cartography from inegi at a 1:50,000 scale, updated by means of a Landsat etm₊ image for the year 2000, and SPOT 5 images for 2004 and 2008. Our analysis has allowed us to determine the time interval in which the general annual change rate was higher; which categories were most active and which latent; which categories were targets of active transitions; and if the pattern of change remained stable through time. We observed a fast annual rate of change between 2000 and 2004, with an absolute change of 70.936 hectares in comparison to the period 2004-2008, which showed a slower rate of change, of 2,194 ha in absolute terms. These results show a deceleration in the overall process of transformation of land use, which could be related to the publication and implementation of the BRSM management plan in 2000, which may have restricted land-use change in the core zones.

At the category level, we found high rates of deforestation of tropical forests to agricultural and livestock production uses, and latency in temperate forests with a slower intensity of transition towards these uses. In this regard, the temperate forests are latent coverages that do not fall in the change intensively in the overall dynamics of change and could mean they are in a state of minor disturbance. However, there might be a degradation process, since in the case of introduction of cattle, this grazing free mainly in the rainy season directly affecting the temperate forest understory.

In terms of change rate, the tropical forests had an estimated -1% per year rate. In contrast, forests showed lower rates of change of -0.5% per year. The land uses change rates such as irrigated agriculture, induced pasture, urban areas and iron mine were above 1% per year, indicating an increase in its surface in both periods. An intensive process of change observed in both periods at the category level is the loss of tropical dry forest. The areas of higher change are located in the buffer and influence zones, where the management plan does not regulate land use. In particular, long-established livestock production activity in the region appears as the driving factor of deforestation, affecting both tropical and temperate forests though at different rates. Finally, the cartography derived from the analysis of intensity of change is a contribution for decision-making concerning the management of the BRSM with emphasis in the buffer zone.