Assessing Distribution Patterns, Extent, and Current Condition of Northwest Mexico Mangroves

Abstract

This study contributes to the worldwide effort to update the status of mangroves, assessing a large mangrove distribution area in Mexico by analyzing Landsat MSS from the early 1970s and TM imagery from 2005. Four states (Baja California Sur, Sonora, Sinaloa, and Nayarit) integrate the northwest region of Mexico, where the mangrove area was estimated to be around 180,000 ha on both dates, with a reduction of about 2% by 2005. Nayarit by itself had a large decrease (>10,000 ha), while the other states increased their mangrove extent from 4 to 15%. However, this increase was probably a consequence of improved satellite capabilities in 2005 rather than mangrove expansion. Mangrove condition, measured through a normalized difference vegetation index (NDVI), was categorized into four types based in the index value distributions. Type 1, representing the poorest condition, included values below the first quartile (Q1), while Type 4, the best condition, was indicated by values above Q3. One of the intermediate categories (Type 3) was dominant, accounting for >40% of the total mangrove surface in both the 1970s and 2005. Mangrove systems in northwest Mexico have different conditions of stress, and thus different management strategies should be identified to preserve and maintain those systems.