Dr. Brower Finds Frozen Milkweed in Florida

March 15, 2010

The following is an update on the status of monarch butterflies overwintering in Mexico as observed from 7-12 March 2010 by Lincoln Brower and our research team, Isabel Ramirez, Dan Slayback and Raul Zubieta.

We arrived in Angangueo on Sunday afternoon, 7 March 2010. The amount of damage due to the unprecedented rainfall that occurred from 31 January - 5 February 2010 is extraordinary.The road down the mountain from the Sierra Chincua field station was badly damaged and severely undercut by erosion in numerous places, and as we turned the bend approaching the upper part of Angangueo, we began to see catastrophic damage to the houses along the creek that runs down through the town.

Examination of our Geoeye satellite image taken on 2 March 2010 indicated that at least two major landslides had occurred in the town: the first was along the south side of the road and had followed the creek running down past the upper mine area, feeding into the main town stream. Immense amounts of dirt and rock were forced westward cross the road into the main stream channel and caused flooding and destruction of numerous houses. The lower floors were filled with dirt, totally destroyed construction material, stumps and were battered by tree trunks left from prior logging.

A bit further down the stream the second major landslide occurred directly perpendicular to and into the main stream, and across the road. This landslide occurred on an extremely steep deforested slope above the main stream, and further examination indicated that the area surrounding the landslide had recently burned. This slide completely obliterated several houses, and the debris carried with it blocked the main stream, causing ever-increasing damage to the downstream houses, land and vehicles. Several of the latter were piled on top of each other and unbelievably flattened. Water and mud and debris also swept through many houses damaging or virtually destroying them. Rocks, mud, household debris was everywhere—mattresses, cd's, kitchen furniture, toys. etc. Pathetic surviving canines still loyally stayed next to deserted homes.

Major damage continued down to the area where the traffic fork occurs above the churches and the town square. At that point, the streambed was wider and could accept most of the debris in the water flow, passing it along the west side of the town. However, about half way down through town, another westward running tributary creek that had been diverted into a channel beneath a prominent citizen's home literally exploded with water and debris. This almost instantly filled the courtyard with several feet of water and came close to drowning two members of the family who were working on the ground floor. The occupants of the house said that their family had lived there for 94 years and had never been flooded. Two popular hotels, the Margarita and the Don Bruno were far enough down and above the creek that they were unscathed. Our reaction to the devastation was profound sadness and a sympathetic sharing of the terror of the event.

Examination of our satellite image indicated numerous other landslides in the Monarch Butterfly Biosphere Reserve. The most amazing and extensive occurred on the north slope of Cerro Pelon where at least seven slides are evident. This area had been clear cut and burned several years ago, as shown in our aerial reconnaissance film. We are currently studying the satellite imagery to determine to what extent poor land use (deforestation, conversion to agriculture on steep slopes and burning) has contributed to the landslides.

Ground reconnaissance on the Sierra Chincua resulted in our finding even more landslides because they were hidden by tree cover in the satellite images. We walked from the bottom of the main stream that leads up to the Sierra Chincua colony area, known as Arroyo Hondo. This has been key monarch overwintering habitat since the area was discovered in 1975. Prior to the storm, the small stream flowed down the mountain and out through agricultural fields at the bottom of the arroyo. Monarchs form their colonies at the headwater branches of this stream, and as the winter progresses, the colonies move down along the stream. By February millions of monarchs fly down the stream bed seeking wet, sunny areas where they can drink water. In 2009, BBC obtained fabulous footage of the drinking butterflies that will be shown in a major TV broadcast in March 2010. The area where they carried out this photography is now unrecognizable. Huge flooding carried increasing amounts of debris (soil, tree trunks that had been illegally logged and rocks, from pebbles to immense boulders) down the stream and its tributaries. The debris flow scoured widely through the valley and down to bedrock. Trees of all sizes growing along the original stream as well as floatsam and jettsom from prior illegal logging operations were carried away by the flooding. The small arroyo that bordered the BBC colony two years ago is now a 30 foot deep canyon on top of bedrock. One of our temperature measuring transects across the stream in an area that was a closed forest area is just plain gone. Fortunately, the butterflies seemed to have fared well enough such that there is still a moderate colony in the undisturbed forest above the eroded areas.

In addition to the water-caused damage, the combination of soil soaking and wind resulted in several areas where variable numbers of oyamel firs and pines were uprooted and toppled. These blow-down areas can be seen clearly in the satellite images. One of the areas is behind Chincua Station (the buildings at the entrance of Chincua where we have done considerable temperature research) had numerous trees fall that have badly damaged this important research area. Another severe tree fall area was along the ridge on the west side of the Sierra Chincua above both Arroyo Hondo and Arroyo Zapatero where butterfly colonies have formed year after year. We were struck by the extreme localization of these tree fall areas. This may have been due to heavy winds that randomly struck certain localized spots within the forest. Statements in the Mexican press have exaggerated the extent of the tree fall damage and we are concerned that it will be used as an excuse to harvest and remove many trees. In our scientific opinion, the downed trees should be left where they fell inside the Reserve and allowed to recycle into the ecosystem.

World Wildlife Fund-Mexico has a research team monitoring monarch mortality in the various colonies. Our non-quantitative observations suggested that the Chincua colony was still in good condition. Observations on the south side Cerro Pelon where the colony formed in a very protected valley were surprising: very little forest damage was evident, no avalanches were seen but we saw only two trees still with butterfly clusters. We know from the WWF-Mexico December report that the Chincua and Pelon colonies were both about 0.5 ha in area. On our last day in the area (12 March), we attempted to visit the Herrada colony that is located to the southeast of The Reserve. However, the local guides (who are very reliable) told us that the colony had left on about 10 March. Thus we think that the Pelon colony was either severely damaged by the storm, or the butterflies have also for the most part prematurely left the area. That both the Pelon and Chincua colonies seemed still in their midwinter phase was indicated by the fact that we observed no major streaming out the colonies.

As published in the WWF-Mexico report, the 2009-2010 overwintering season began with the lowest number of butterflies seen in the past 16 years. On top of this, the prolonged storm included heavy hail seems to have damaged and dispersed many of the monarchs. It is likely that the original 1.92 hectares of monarchs has been reduced by at least 50%. We hope that what will be the all time historical low number of surviving butterflies will meet good weather conditions when they fly into Texas to reestablish the new spring generation at the end March and early April.