Degradation of the oyamel fir‐pine forest ecosystem in central Mexico is a threat to the overwintering and migratory phenomenon of the eastern North American population of the monarch butterfly ( Danaus plexippus). Because a lack of quantitative data has hindered effective conservation policy, we photogrammatically analyzed the changing state of a major overwintering forest area. We analyzed stereographic aerial photographs of a 42,020‐ha area taken in 1971, 1984, and 1999 with GRASS, a geographic information system. What in 1971 was a nearly continuous high‐quality forest is now fragmented and severely degraded. Between 1971 and 1999, 44% of conserved forest ( forest with>80% cover) was degraded, and the largest patch of high‐quality forest was reduced from 27,115 ha to 5827 ha. The annual rate of degradation from 1971 to 1984 was 1.70%, and this increased to 2.41% during the next 15 years. At the latter rate, <10,000 ha of high‐quality forest will remain in 20 years and <4,500 ha in 50 years. A subset of the analysis quantified changes in a 6596‐ha area on the Sierra Chincua, Sierra Campanario, and Cerro Chivati Huacal massifs that were declared protected by presidential decree in 1986. Corresponding rates of degradation of these reserves more than tripled, from approximately 1.0% between 1971 and 1984 to more than 3% between 1984 and 1999. Passage of the 1986 decree failed to protect the forest. Our data provide irrefutable evidence that successful implementation of a more inclusive presidential decree issued in November 2000 will require (1) effective enforcement against logging within the oyamel‐pine forest ecosystem and (2) restoration of areas that have been degraded. All indications are that the rate of logging is increasing throughout the area. The grandeur of the monarch butterfly overwintering phenomenon in this tiny area of Mexico is too great a cultural and biological treasure for this rampantly destructive process to continue.
Expert consultation has been used to fill the information gaps that hamper conservation planning and nature reserve design. The use of expert knowledge in conservation planning is difficult, however, because it is subjective, biased, and value‐laden. Decision theory provides a systematic and comprehensive means for addressing experts' subjective—and sometimes contradictory—judgments in the design of nature reserves. Thus, the experts can separate the objective criteria from the subjective components of decision making that place value on those criteria. When linked to a geographic information system ( GIS ), these techniques foster consensus among experts by allowing the exploration of alternative designs in an iterative way. We used such a decision‐analysis approach to redesign the Monarch Butterfly Biosphere Reserve ( MBBR ) in central Mexico. We examined three reserve scenarios to identify the optimal overwintering habitats considering ( 1 ) an area equivalent to the previously defined boundaries of the core zone of the MBBR ( 4500 ha ); ( 2 ) an area equivalent to the previously defined boundaries of the whole MBBR ( 16,000 ha ); and ( 3 ) the maximum possible extent for a new core zone. This last scenario produced an area of 21,727 ha. These results were transferred to the GIS to create the respective nominal maps that were presented to the environmental authorities, who selected the third scenario for the core zone of the new MBBR. Our results allowed us to locate the prime overwintering habitats precisely and to delimit a core area for the reserve that would minimize the inclusion of forest stands valuable to local loggers.
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