Response to Large Scale Natural Disturbance in Southern Yucatán

I.    New knowledge about ecosystem-level response to increased frequency of large-scale natural disturbance driven by climate change

Quantify and map regional forest damage resulting from Hurricane Dean

Through the use of remotely sensed imagery, geographic information systems, and field survey assessments, we have produced a map of estimated damage resulting from Hurricane Dean across the study region. (Rogan, Schneideret al., 2011)

High Mortality for Rare Species Following Hurricane Disturbance in the Southern Yucatan (Vandecar et al., 2011)

Hurricanes are an important part of the natural disturbance regime of the Yucatan Peninsula with the potential to alter forest structure and composition, yet investigations of species-level responses to severe winds are limited in this region. Species varied in the degree and type of damage experienced, with susceptibility increasing with tree diameter and height. Wood density influenced damage patterns only in areas where a critical threshold in storm intensity was exceeded. Although overall, damage severity increased with wind speed, common coastal species were more resistant to damage than species distributed farther inland. Our findings suggest that selective pressure exerted by frequent hurricane disturbance has, and will, continue to impact the floristic composition of forests on the Yucata´n Peninsula, favoring certain wind-resistant species. (Vandecar et al., 2011)

Damage patterns after Hurricane Dean in the southern Yucatán: Has human activity resulted in more resistant forests? 

We investigated how patterns of hurricane damage were related to windspeed, stand characteristics, and land use in a region where forest composition and structure have been strongly influenced by human activities. Land use in the corridor has altered both landscape and forest stand structure. Compared to the upland protected areas, forests in the study area were significantly shorter and characterized by smaller stems. Nine months after the hurricane we assessed the damage in a set of 91 plots to test the effect of local stand structure on hurricane resistance. Despite the strength of the storm, on average 27% of stems at the stand level showed no signs of damage and only 5% across the study were killed by the hurricane. In step-wise linear regression models, 13 to 52% of the variation in 
damage frequency was accounted for by windspeed and stand structure. 

Canopy height, basal area and median dbh were significant predictors. For moderate to severe damage classes, measures of stand size were generally positively correlated with damage frequency suggesting that stands with higher canopies and/or greater basal area or median dbh suffered the most during this storm event. A land-use history including clearing in the previous 30 to 50 years was associated with significant decreases in stand basal area, median dbh and canopy height as well as frequency of specific damage classes within the dominant forest type. (Paper submitted to Forest Management and Policy)

Investigate household responses, social impacts, vulnerability, and adaptability

350 individual surveys regarding the vulnerability and adaptability of communities were undertaken in the 22 communities where forest damage data was collected, during September to December of 2008. Most households stated that they are not abandoning subsistence cultivation because of the hurricane, but for a few farmers, the hurricane is seeing as the “last drop” after a long story of low harvests and low prices. Milpa (maize) production, even for subsistence, is becoming increasingly difficult because of several factors: according to many informants an ongoing drought since 1998, insufficient attention of the rural sector.

II.    Increased scientific and technical capacity of public agencies and protected area managers at Calakmul and Sian Ka'an Biosphere Reserves to establish and employ science‐based approaches and techniques for long‐term forest management following large‐scale disturbance

1.    Conceptualizing the Corridor—Presentations by Dr. Laura Schneider and Dr. John Rogan discussed the social and ecological landscape structures, and Dr. Ann Snook of The Nature Conservancy discussed previous and ongoing projects across the region. Of special focus was the way in which the phenomena of interest may vary based on the scale of analysis and how the manifestation of landscape pattern is a function of many nested processes

2.    Remote Sensing Possibilities and Limitations—Presentations by Drs. Rogan and Christman discussed the potential for using standardized mapping methodology over diverse landscapes, as well as the potential limitations for accuracy and thematic detail.

3.    Remotely Sensed Data Acquisition and Use—Tools for the analysis of fire and vegetation were presented by EDGY team members, and representatives from the INEGI‐ERIS Satellite receiving station offered an overview and tour of the facilities and processes.