Cauca Valley dry forests

The Apure-Villavicencio dry forests stretch along the eastern foot of the Andes' eastern cordillera, spanning the Venezuelan states of Portuguesa, Barinas and Apure and the Colombian departments of Arauca, Casanare and Meta. This is a transitional ecoregion, a patchwork of premontane, gallery and deciduous dry forest grading into savanna where the Andean montane forests give way to the lowland Llanos grasslands. Characteristic woody plants include mesquite (Prosopis juliflora), palo verde (Cercidium praecox), kapok (Ceiba pentandra), yellow mombin (Spondias mombin), and palms such as the moriche (Mauritia flexuosa) and macaúba (Acrocomia aculeata). Its climate is equatorial with a pronounced dry winter (Köppen Aw), with temperatures ranging from about 19 to 33 degrees Celsius. The forests have been severely degraded by deforestation, farming and ranching, leaving poorly protected remnants that the World Wildlife Fund rates as Vulnerable, yet they still shelter the giant anteater, Geoffroy's spider monkey, and the flagship Colombian four-eyed frog. Gardeners may recognize several natives here as ornamentals, including the stately kapok tree and the moriche and macaúba palms.

The Bajío dry forests cover the southwestern Mexican Plateau in west-central Mexico, spanning the states of Jalisco, Guanajuato, and Michoacán across the Lerma River basin and the lake country around Chapala, Cuitzeo, and Pátzcuaro. Set in valleys between roughly 1,000 and 2,000 meters on shallow, rocky, well-drained volcanic and limestone soils, the region was historically dry deciduous forest whose characteristic trees included copal, pochote, palo amarillo, and mauto, with thorn-scrub communities of mesquite and huamúchil. The climate is tropical subhumid, with annual rainfall around 500 to 930 millimeters and a pronounced dry season that can last up to eight months. This is one of Mexico's most developed and densely populated landscapes, and centuries of agriculture and grazing have reduced the forest to small pockets now dominated by thorn scrub and subtropical matorral, leaving the ecoregion classed as critical or endangered with only about 7.5 percent in protected areas. Gardeners working in comparably dry, seasonal climates may recognize natives of this region in drought-adapted, deciduous trees such as mesquite and copal.

The Balsas dry forests occupy the basin of the Balsas River in western and central Mexico, spreading across the states of Michoacan, Guerrero, Morelos, Mexico, Puebla, and Oaxaca. This tropical dry broadleaf ecoregion is a deciduous and thorn forest dominated by Bursera trees, alongside the legume Haematoxylum brasiletto and abundant columnar cacti such as Pachycereus and Cephalocereus. The climate is tropical and subhumid, with seasonal rainfall and a severe dry season that can last up to eight months. The forests are a renowned center of plant endemism and speciation, especially for Bursera, with roughly half of the region's Bursera species found nowhere else, and they shelter the near-endemic Balsas screech-owl, though only about a tenth of the ecoregion lies within protected areas. For drought-tolerant or xeric plantings, the native Bursera (the source of copal incense) and the dyewood Haematoxylum brasiletto are ornamental genera that evolved here.

The Bolivian montane dry forests occupy the eastern flank of the Andes in south-central Bolivia, barely reaching into northwest Argentina, where they form a transitional band between the moister Yungas and high puna grasslands above and the lowland Chaco scrub below. Across rugged terrain of cliffs, steep hillsides, and river valleys, the vegetation is a xeric mosaic of dry slopes studded with scattered shrubs and columnar cacti, seasonal dry forest, and gallery forest along watercourses, with characteristic woody plants including Vachellia caven, hopseed bush (Dodonaea viscosa), Prosopis, and quebracho hardwoods such as Aspidosperma quebracho-blanco and Schinopsis. The climate is strongly seasonal and semi-arid, pairing a pronounced dry winter with summer rains. The World Wildlife Fund rates the ecoregion Critical/Endangered, as only about six percent of its original habitat remains amid fragmentation from urban sprawl, agriculture, overhunting, and fuelwood cutting; it nonetheless shelters numerous endemic birds, among them the Bolivian blackbird, Cochabamba mountain finch, and the endangered red-fronted macaw, with the torrent duck as a flagship species. For gardeners in dry, mild-winter climates, several of its natives, such as the ornamental hopseed bush and the fragrant-flowered Vachellia caven, are familiar landscape plants.

The Brazilian Atlantic dry forests form a tropical dry forest ecoregion of eastern Brazil, stretching across northern Minas Gerais, Bahia, and Piauí along the São Francisco River depression, where they sit between the Cerrado savannas of central Brazil and the Caatinga dry shrublands of the northeast. The vegetation is deciduous to semi-deciduous forest reaching roughly 25 to 30 meters tall, characterized by trees such as the bottle-trunked barriguda (Cavanillesia arborea), Brazilian cedarwood, and Tabebuia species. The climate is tropical with a pronounced dry season of about five months and annual rainfall of 850 to 1,000 mm, on eutrophic soils derived from Bambuí limestone. Conservation is a serious concern: around 70 percent of the native forest has been cleared for agriculture and charcoal production tied to Brazil's steel and pig-iron industries, and the region is home to the critically endangered Barbara Brown's titi as well as threatened birds like the hyacinth macaw. For gardeners, the native Tabebuia trumpet trees are familiar ornamental flowering trees rooted in this drought-adapted flora.

The Caatinga is a semi-arid ecoregion covering the drier interior of northeastern Brazil, stretching across states including Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe, Bahia, and parts of Minas Gerais, and it ranks as the largest dry forest region in South America. Its vegetation is a heterogeneous xeric shrubland and thorn forest of small, drought-deciduous thorny trees, with a ground layer rich in cacti and succulents such as the mandacaru (Cereus jamacaru) and prickly pears (Opuntia), alongside carnaúba palms and fruit-bearing trees like umbú. The climate is hot and dry, with six to eleven dry months a year and average annual rainfall ranging from about 250 to 1,000 millimeters. Despite this aridity, the Caatinga harbors a unique biota with many endemic species and is the home of its flagship bird, the Spix's macaw (Cyanopsitta spixii), though less than seven percent of the ecoregion is currently protected. For gardeners in hot, dry climates, its native cacti such as Opuntia and Cereus are familiar ornamental and edible-fruit genera.