The thicket It is a fascinating and extremely diverse ecosystem, characterized mainly by the predominance of low-growing shrubs and bushes, which form dense plant formations and constitute essential habitats for numerous species of both flora and fauna. These systems, which range from arid regions to humid mountains, play a crucial role in ecological regulation, conservation of the biodiversity and environmental balance.
What is a scrubland? Definition and ecological context
Un scrub It is a terrestrial plant formation where shrubby vegetation predominates, with low-growing woody plants, generally less than 4 meters tall, accompanied by herbs, grasses, geophytes, and, to a lesser extent, small trees. These ecosystems can be natural or the result of human intervention, and their development depends on factors such as climate type, altitude, soil composition, and the environmental history of the location. They are found in a wide variety of contexts, from arid, semi-arid, and desert areas to temperate, coastal, Mediterranean, and high-mountain environments in tropical regions.
Essential characteristics of the scrubland
- Dominant vegetation: Mainly low-growing woody shrubs, accompanied by herbs and grasses, with few small trees.
- Level: Shrub species vary in size, from 0.5 to 4 meters, depending on the type of shrub and its geographical location.
- Adaptability: They exhibit remarkable adaptations to drought, nutrient-poor soils, high levels of sunlight, and, in many cases, resistance to recurrent fires.
- Diversity: They exhibit an extraordinary variety of plant and animal species, the composition of which depends on the climatic region, altitude, and human intervention.
- Relief and location: They develop from sea level to altitudes close to 4000 meters, in plains, valleys, slopes and mountainous areas.
- Eco-friendly function: They control erosion, contribute to nutrient cycling, provide shelter and food, and are essential for pollination and seed dispersal.
Types of scrublands: ecological and geographical diversity
The great versatility of shrublands means they are found in different regions of the world, adapting to diverse climates, from the most arid to the coldest and most humid mountain climates. The main types of shrublands are classified according to the prevailing climate and the main flora that characterizes them.
- Xerophilous scrub: Found in arid and semi-arid areas with low rainfall and high temperatures. The plants are drought-resistant, generally succulent, with small, spiny or fleshy leaves.
- Mediterranean scrubAssociated with temperate climates with dry summers and mild, rainy winters. Aromatic shrubs, perennial woody species, and bushes adapted to fire and water scarcity predominate.
- Moorland scrubLocated in high mountain tropical regions, its vegetation is adapted to the cold, intense solar radiation, and daily temperature fluctuations.
- Secondary and anthropized scrublands: Formed by the alteration or degradation of forests and natural areas, often due to human action (deforestation, agriculture, grazing).
Subtypes and regional examples of scrublands
- Microphyllous desert scrub (tiny leaves): Present in regions such as northern Mexico, dominated by species with very small and thorny leaves.
- Sarcocaule and sarco-crasicaule thicket (thick, fleshy stems): Common in areas where species such as palo verde, elephant's foot, or columnar cacti predominate.
- Rosette scrub (rosette leaves): Characteristic in particular soils, with agaves and similar plants.
- Submontane and subtropical scrub: Dominated by mesquites, huizaches and other legumes in transition zones between desert and forest.
- Thickets of halophilous and gypsophilous vegetation: Adapted to saline or gypsum soils, with highly specialized species.
Climate and soils in scrubland ecosystems
Shrubs develop under highly variable environmental conditions. In arid and semi-arid areas, climates with rainfall of less than 700 mm per year, long dry periods, and temperatures that can range from 12 to 26°C predominate. The soils are usually poor in organic matter, stony, sandy and with low water retention, although there may be exceptions in mountainous areas or areas with coastal influence.
Processes of formation and evolution of the scrubland
There are two main processes by which thickets are formed:
- Natural formation: When environmental conditions prevent the development of a dense forest (aridity, extreme climate, poor soils).
- Secondary education: It results from the degradation of original vegetation due to fires, overgrazing, logging, or agricultural practices. In these cases, scrubland may be a temporary or even permanent state if conditions do not allow for restoration of the original ecosystem.
Characteristic flora of the scrublands
The vegetation of the scrublands is extremely varied, and depends on both the local climate and the evolutionary history of the region. The following are the most representative plants of each type of bush:
Xerophilous scrub
- Succulents and cacti: Columnar cacti (pitayo, cardón, old cactus, star cactus), agaves, yuccas, and other species with tissues capable of storing water, such as salsola vermiculata.
- Thorny bushes: Governor (Larrea tridentata), mesquite (Prosopis juliflora), green stick (Parkinsonia microphylla), bull (Bursera microphylla), elephant's foot (Beaucarnea gracilis), pincers (Havardia pallens), candle (Fouquieria columnaris), copalquin (Pachycormus discolor), ironwood (Olneya tesota).
- Drought-resistant grasses and herbs.
- Halophytic and gypsophilous plants: Adapted to saline or gypsum soils, such as the mat (Abronia maritima), chamiso (Atriplex canescens), rheumatic herb (Frankenia gypsophila), lomboy (Jatropha cinerea), romerito (Suaeda spp.), purslane (Sesuvium spp.), glass (Batis maritima).
Mediterranean scrub
- Evergreen and aromatic shrubs: Rosemary (Rosmarinus officinalis), thyme (Thymus vulgaris), lavender (Lavandula spp.), heather (Erica spp.), rockrose (Cistus spp.).
- Woody bushes and small trees: Oak (Quercus ilex), cork oak (Quercus suber), wild olive (Olea europaea sylvestris), mastic (lentiscus pistachio), myrtle (myrtle common), jujube (ziziphus lotus).
- Plants adapted to fire: Species capable of re-sprouting after fires thanks to resistant seeds or radical regrowth.
- Endemic species by region: For example, argan (Argania spinosa) in Morocco, South African fynbos (Proteaceae, Ericaceae, Restionaceae), Australian kwongan (Myrtaceae, Fabaceae).
Moorland scrub (high mountains)
- Grasses, Asteraceae and Orchidaceae: Species such as frailejones (espeletia), Asteraceae (Pentacalia, Hinterhubera, Culcitium), tiny orchids and various composites.
- Shrubs and low bushes: Plants covered with dense hairs, rosette leaves, adaptations to intense cold and solar radiation.
Other common species in scrublands according to adaptation
- Plants with small, leathery or thorny leaves to reduce transpiration and water loss.
- Plants with water storage capacity or deep root systems.
- Herbivore-resistant plants thanks to thorns, bitter substances or toxins.
Scrubland fauna: adaptations and representative species
La scrubland fauna It presents a rich diversity, composed of mammals, birds, reptiles, amphibians and invertebrates, each with specific adaptations to the particular conditions of these ecosystems.
Xerophilous scrub
- Mammals: Coyote (Canis latrans), Wildcat (Lynx rufus), black-tailed jackrabbit (Lepus californicus), raccoon (Procyon lotor), puma (Puma concolor), badger (Taxidea taxus), northern vixen (Vulpes macrotis), mule deer (Odocoileus hemionus), bats and peccaries.
- Birds: Red-tailed Hawk (Buteo jamaicensis), great horned owl (bubo virginianus), burrowing owl (athene cunicularia), macaws (Piazza military), roadrunner (Geococcyx velox), desert woodpecker (Melanerpes uropygialis), Mexican falcon (Falco mexicanus), golden eagle (Aquila chrysaetos), bearded caracara (Caracara cheriway).
- Reptiles and amphibians: Lizards (Aspidoscelis parvisocia, Xenosaurus rectocollaris), green lizard, spiny tortoise, Bolson turtle (Gopherus flavomarginatus), rattlesnakes (Crotalus atrox, C. lepidus, C. molossus, C. scutelatus), coralillo (Micrurus pachecogili).
- Invertebrates: Scorpions, ants, bees, butterflies, spiders and a wide range of adapted beetles.
Mediterranean scrub
- Mammals: Fox (Vulpes vulpes), rabbit, wild boar, deer, mountain goat, Iberian lynx, Iberian wolf, Cretan goat (kri-kri), Cretan spiny mouse.
- Birds: Birds of prey such as eagles, hawks, owls, woodpeckers, thekla lark, Dupont's lark, wading birds and small birds.
- Reptiles: Lizards, snakes, Moorish tortoise (Testudo graeca soussensis).
- Insects and pollinators: Butterflies, bees, beetles and ants are essential for pollination and seed dispersal.
Moorland scrub
- Mammals: Spectacled bear (Tremarctos ornatus), puma, white-tailed deer, rabbit, mouse, cururo, moor cat (Felis colocolo), White-tailed deer (Odocoileus virginianus).
- Birds: Condor (Vultur gryphus), hummingbirds, eagles, guacharaca, troupial.
- Reptiles and amphibians: Lizards adapted to cold and altitude.
- Invertebrates: Butterflies, beetles, pollinating insects.
Specific fauna according to region and threats
In the bushlands of other continents, iconic species such as the southern guanaco in South America, the zebra and oryx in Africa, the small rockhopper antelope in the South African fynbos, and marsupials such as the nulbengar in Australia are found. Many of these species are under threat due to habitat loss, poaching, and ecological fragmentation.
Adaptations of the fauna and flora of the scrubland
- Drought resistance: Ability to obtain water from food, reduce activity during heat, waterproof skin in insects and scales in reptiles.
- Fire strategies: Resistant seeds, post-fire regrowth, thick bark.
- Thermal insulation in the mountains: Dense fur, accelerated metabolism, social behaviors to share heat.
- Migrations and mobility: Many birds and mammals make seasonal or daily movements in search of food and water.
Environmental services and ecological functions of the scrubland
- Nutrient regulation, pollination and biological control.
- Habitat and fundamental shelter for endemic or endangered species.
- Production of food, fuel, medicinal, textile, and ornamental resources.
- Support for cultural, scientific, recreational and educational activities.
- Carbon sink and climate change mitigation.
Threats and conservation of scrublands
El uncontrolled grazing It is one of the main threats, along with deforestation, agricultural and livestock expansion, overexploitation of resources, and urbanization. Soil compaction and erosion, excessive extraction of plant and animal species, and habitat fragmentation are causing the accelerated degradation of these ecosystems worldwide. Hunting and industrial exploitation have led to the critical decline of some emblematic animal populations such as the pronghorn, bighorn sheep, indigo macaw, and the Iberian lynx.
La scrubland conservation It has become an ecological priority, not only for its biodiversity, but also because nearly 60 million hectares in countries like Mexico offer the natural conditions to support these ecosystems, although many have been transformed into agricultural land or have suffered irreversible degradation. Several protected areas, national parks, and biosphere reserves include significant expanses of scrubland.
Socioeconomic importance: agriculture, livestock and resources
- Agriculture: Although they are not optimal soils, they are used for crops resistant to Mediterranean areas (olive trees, vegetables), as well as for extensive grazing of goats, sheep and, in some cases, cattle.
- Cattle raising: Lower animal population compared to other areas, but crucial for rural economies.
- Resource Extraction: Firewood, timber, aromatic essences, gums, textiles and medicinal plants. For example, latex from the mastic or the oils of Mediterranean myrtle.
- Tourism and environmental education: Ecotourism and recreational activities are booming in many scrubland parks, such as Cabo de Gata in Spain, the Australian Kwongan, and the Andean paramos.
Global examples of scrublands and their biodiversity
- Cabo de Gata-NÃjar Natural Park (Spain): It covers volcanic and arid areas with Mediterranean scrub, cornicoles and mastic forests.
- Souss-Massa National Park (Morocco): Protects succulent thickets of acacia and argan trees.
- Baviaanskloof Mega Reserve (South Africa): It includes fynbos, one of the regions with the highest number of endemic species of plants and small mammals.
- Mucubajà Lagoon (Venezuela): High-altitude moorland scrubland, with species adapted to radiation and cold.
- Caatinga (Brazil), Arid Chaco (Argentina), Californian chaparral (USA), Australian kwongan, among others: All of these are home to extremely rich, but highly threatened, flora and fauna.
Role of climate change and adaptation strategies
- Vulnerability: The scrub, especially those in arid and semi-arid areas, are extremely sensitive to rising temperatures, reduced rainfall, frequent fires, and changes in weather patterns.
- Adaptation strategies: Restoration of native vegetation, fire control, sustainable water management, crop diversification, scientific research, and environmental education.
- Mitigation: Promotion of renewable energy, reduction of deforestation, agroecological practices, and conservation of natural carbon sinks.
