# Tropical Dry Forest Diversity, Climatic Response, and Resilience in a Changing Climate
## 1 Introduction  
Changes in climate are heavily impacting both natural and developed areas in Central and South America [1; 2; 3]. Over the past five decades, climatic phenomena have been responsible for 88 percent of disasters, globally [4]. These climatic disasters include increases in hurricanes and tropical storms in areas that have previously not seen this scale of storm, as well as increases in droughts and flooding due to extreme El Nino and La Nina events [1; 2; 5; 6]. Climatic changes have impacted biomes around the globe, with recent increases in disturbance decreasing ecosystem recovery rates and variations to precipitation and temperature which directly impacts forest phenology, flowering rates and times, photosynthesis, water use, and nutrient transport. The changes that occur in tropical dry forests (TDFs) is of particular interest as the countries in which they are located house high population densities and much of the forest is converted for agriculture and cattle [7; 8]. TDFs encompass 42% of the tropical forest regions and have focal points in Central and South America, Africa, Central Asia, India, and Australia [8; 9; 10]. Only 2% of the TDFs are intact and only 8% are legally protected [7; 10], but they contain high levels of biodiversity, with 12 distinct floristic groups in the Central and South American TDF and the number of unique tree species in stands ranging from 100 at high latitudes to over 1000 near the equator [11; 12; 13]. Additionally, between 50% and 75% of the remaining TDF is thought to be located in Central and South America, predominantly in Mexico, Bolivia, and Brazil [14; 15] (Figure 1). An area with a mean annual temperature \(>\)25 \({}^{\circ}\)C, precipitation between 700-2000 mm with a dry season of \(<\)100 mm for at least three months, which comprises \(>\)50% deciduous trees, defines the TDF ecosystem [16]. Additionally, TDFs are water-limited and have high biodiversity typified by trees, lianas, shrubs, herbs, graminoids, and bromeliads [17]. Tropical dry forests have the third highest deforestation rate globally and are subject to high anthropogenic alteration [14; 18; 19]. Much of this deforestation is due to high population densities, which creates a predominantly fragmented landscape [14; 20]. The high population densities in TDFs are due to climate, geography, and a high number of neotropical freshwater sources [21]; however, despite its regional and global importance, it remains severely under-studied relative to the humid forest [22]. Only 14% of tropical forest scientific papers, until 2005, focused on tropical dry forests, with a heavy emphasis on Costa Rica, Mexico, and Brazil [14; 16; 23]. Since 2005, research into TDFs has been increasing but it still only comprises less than 25% of research into tropical forests annually (Figure 2). Figure 1: Location of the tropical dry forests (TDFs) in Central and South America. The dry ecosystems also include the Brazilian Cerrado (savanna) and Caatinga (Data from [PERSON] and [PERSON] 2010; photos from [PERSON]). Much of the TDFs in Central and South America remain unprotected, highly fragmented, and at risk of being cleared [14]. In Brazil, for example, more than 90% is comprised of secondary forests, which have recovered after being cleared or burned for agriculture [19; 24]. In contrast, Costa Rica is an exception where legislative, social, and economic changes have led to regeneration rates exceeding current deforestation rates [25; 26]. Conservation strategies, aimed to protect TDFs in different countries have ranged from the implementation of payments for ecosystem services to the creation of conservation areas and community-based management systems [25; 27]. The degradation and anthropogenic protections detailed above do not take into account forest alteration under climatic change.