Shrublands are not defined by a single climate but by a shared structural outcome: landscapes dominated by woody plants that rarely exceed a few meters in height, shaped by some combination of drought, fire, poor soils, or cold that prevents forests from taking hold. They span an enormous range of climates, from the sun-baked chaparral of California to the wind-scoured dwarf willows of the Arctic. What unites them is less about temperature or rainfall totals and more about seasonal stress and how plants respond to it. Understanding where shrublands occur and why requires looking at each major type on its own terms.
Mediterranean Shrublands and the Dry-Summer Pattern
The most studied shrubland climate is the Mediterranean type, characterized by warm, dry summers and cool, wet winters. This seasonal pattern occurs in five widely separated regions around the world: the Mediterranean Basin itself, California, central Chile, the Cape Region of South Africa, and southwestern Australia.1Trends in Ecology & Evolution. Plant diversity in Mediterranean-climate regions These five regions sit at roughly similar latitudes, generally between about 30° and 40° from the equator, on the western sides of continents where cold ocean currents and subtropical high-pressure systems conspire to suppress summer rain.2Annual Review of Ecology, Evolution, and Systematics. Mediterranean Biomes: Evolution of Their Vegetation, Floras, and Climate
Annual rainfall in these areas typically falls between about 250 and 900 millimeters, with most of it arriving in winter. Summer temperatures often exceed 30 °C, and the combination of heat and months without rain creates intense water stress. Plants in these shrublands have evolved a distinctive suite of traits to cope: tough, waxy, evergreen leaves (a condition called sclerophylly), deep root systems, and the ability to go semi-dormant during the driest months. The resulting vegetation goes by different local names: chaparral in California, maquis or garrigue around the Mediterranean, fynbos in South Africa, matorral in Chile, and kwongan in Australia. Despite different species, the structural resemblance across continents is striking.
The seasonal rhythm of rain followed by drought also makes these shrublands highly fire-prone. Vegetation grows vigorously during the wet season, then dries to tinder by late summer and early fall, precisely when conditions are hottest and driest. Many Mediterranean shrub species are not just fire-tolerant but fire-dependent, regenerating from underground root crowns or releasing seeds that germinate only after exposure to heat and smoke.
Arid and Semi-Arid Shrublands
Not all shrublands have a neat wet-and-dry seasonal flip. In arid and semi-arid regions, the defining feature is simply that there is not enough water, in any season, for trees to dominate. The Great Basin of the western United States is a sprawling example: an arid region with enormous spatial and temporal variability in rainfall, dominated by sagebrush steppes where various species of Artemisia shrubs and perennial bunchgrasses form the largest rangeland ecosystem in North America.3Europe PMC. Challenges and limitations to native species restoration in the Great Basin, USA Annual precipitation can be as low as 150 millimeters in some valleys and over 400 millimeters at higher elevations, but much of it arrives as snow. Summers are hot and dry; winters are bitterly cold. The combination of temperature extremes and low moisture creates conditions where only shrubs, grasses, and sparse forbs can persist.
Similar arid shrublands occur across central Asia, the Middle East, interior southern Africa, and the drier portions of Australia’s outback. In the Negev Desert, for instance, shrubs play a surprisingly active role in modifying their surroundings. Measurements show that the soil surface beneath shrub canopies can be more than 14 °C cooler than exposed ground in summer, and the shaded ground retains moisture for days longer after a rainstorm. In one study, vapor pressure beneath the canopy reached about 2.2 kPa compared with less than 0.9 kPa on the exposed ground nearby.4Earth Surface Processes and Landforms. The effect of shrub canopy upon surface temperatures and evaporation in the Negev Desert That extended wetness under the canopy matters for every organism sheltering there, from soil microbes to seedling plants. Shrubs in arid environments function as small-scale climate engineers, creating pockets of cooler, moister habitat in otherwise hostile terrain.
Tropical and Subtropical Dry Shrublands
In the tropics, shrublands emerge where consistently high temperatures meet low or extremely variable rainfall. The Caatinga of northeastern Brazil is the largest block of tropical dry forest and woodland in South America, and its drier stretches grade into open shrubland. Unlike Mediterranean systems where winter is wet and summer is dry, the Caatinga faces year-round heat coupled with seasonal drought and, critically, high year-to-year rainfall variability that can produce several consecutively dry years.5PLoS ONE. Aridity drives plant biogeographical sub regions in the Caatinga, the largest tropical dry forest and woodland block in South America That unpredictability is arguably more stressful than a predictable dry season, because plants cannot “prepare” for droughts that last one year versus three.
The vegetation responds accordingly. Many Caatinga shrubs and small trees are deciduous, shedding their leaves entirely during drought to conserve water. Succulents, including cacti, are common in the driest zones. Thorny stems help deter herbivores looking to steal moisture-rich tissue. Soils tend to be shallow and nutrient-poor, further limiting tree growth and favoring the scrubby, open canopy structure that defines shrubland. Similar tropical dry shrublands occur across the Horn of Africa, parts of the Indian subcontinent, and northern Australia.
Arctic and Alpine Shrublands
At the other end of the temperature spectrum, shrublands exist above the tree line in mountains and across the Arctic tundra. Here, cold rather than drought is the main constraint on plant size. Dwarf birch, willow, and alder species grow low to the ground, rarely exceeding knee height, hugging the thin layer of warmer air near the surface. Growing seasons are short, sometimes only six to eight weeks, and winter temperatures can plunge well below −30 °C. Permafrost beneath the soil limits root depth and drainage.
These high-latitude shrublands are changing fast. Research in the Canadian Rockies found that willows and other shrubs are advancing upslope, with recruitment rates of roughly 20 individuals per hectare per decade and shrub cover increasing by about 5% per decade at monitored sites. Annual growth of willows tracked summer temperatures closely, while pulses of new seedlings were linked to warmer winters.6Journal of Ecology. Climate warming as a driver of tundra shrubline advance The pattern has been documented across much of the circumpolar Arctic: as temperatures rise, shrubs colonize areas that were previously open tundra, a process researchers call “shrubification.”
That expansion creates a feedback loop. Taller, denser shrubs are darker than the pale tundra grasses, mosses, and snow they replace, meaning they absorb more solar energy. One analysis estimated that undetected erect-shrub expansion in the high Arctic could reduce surface albedo by 0.03 and produce a local summer warming effect of about 5.8 watts per square meter.7Journal of Geophysical Research: Biogeosciences. Challenges in Detecting High‐Arctic Shrub Expansion From Optical Remote Sensing: Implications for Albedo and Climate Forcing In other words, shrub expansion amplifies the warming that caused it in the first place, making Arctic shrublands one of the climate zones where the vegetation is actively reshaping its own climate trajectory.
Fire, Wind, and the Climate of Burning
Fire is so integral to many shrubland climates that you cannot understand the vegetation without understanding the fire regime. In the Great Basin sagebrush steppe, wildfire hazard is highest when a year or two of above-average moisture, which fuels dense plant growth, is followed by a dry winter and spring that cures that fuel into flammable material.8Rangeland Ecology & Management. Where There’s Smoke, There’s Fuel: Dynamic Vegetation Data Improve Predictions of Wildfire Hazard in the Great Basin The wet-then-dry sequence matters more than simply being in a dry year, because without the prior wet period there is not enough fuel to carry a large fire.
In southern California’s chaparral, hot, dry offshore winds are the dominant driver of the most destructive fires. Detailed wind simulations spanning nearly a decade successfully predicted the locations of the largest historical wildfires in the region’s chaparral ecosystems.9Geophysical Research Letters. Spatial variation in extreme winds predicts large wildfire locations in chaparral ecosystems Among all variables studied, low relative humidity was the single strongest predictor of how much area burned per day, while wind speed was especially important on the first day of a fire, when strong gusts push flames across the landscape before containment efforts can take effect.10PubMed Central. Santa Ana winds and predictors of wildfire progression in southern California
Climate projections suggest this fire-weather coupling will intensify. High-resolution modeling of Santa Ana winds under future warming scenarios indicates that increased vapor pressure deficit will further exacerbate wildfire risk over coastal Southern California.11Geophysical Research Letters. Projected Response of Santa Ana Winds Over Southern California to Global Warming by a High‐Resolution Climate Model For residents and land managers in shrubland regions, the climate of fire is not a historical curiosity but an accelerating reality.
Fog as a Hidden Climate Input
Coastal shrublands sometimes benefit from a moisture source that does not show up in standard rainfall measurements: fog. Along the California coast, summertime fog rolls in from the cold offshore current and coats plant surfaces with fine droplets. This fog deposition slowed the rate at which sage scrub species lost moisture in their live tissues during the dry season, though it did not have the same effect on denser chaparral species that grow slightly farther inland where fog is less consistent.12Ecosphere. Fog and live fuel moisture in coastal California shrublands Because drier live fuel burns more readily, fog does double duty: it keeps plants healthier during summer drought and reduces their flammability during the peak fire season.
Several coastal shrub species can absorb water directly through their leaves during overnight fog events, though the efficiency of this foliar uptake varies with leaf shape, hairiness, and how water-stressed the plant already is.13PubMed. Foliar uptake of fog in coastal California shrub species In Chile’s coastal desert, shrubs perform a complementary trick underground: they move water from wetter, deeper soil layers to drier, shallower ones through their root systems at night, a process called hydraulic lift. This allows them to stay metabolically active through the prolonged drought that defines the Chilean desert climate.14Journal of Arid Environments. Hydraulic lift in three shrub species from the Chilean coastal desert Both fog capture and hydraulic lift illustrate how shrubland plants do not merely endure their climate but actively exploit subtle water sources that larger trees, with their greater water demands, cannot rely on.
What Holds Shrubland Soils Together
The soil beneath shrublands is often as interesting as the plants above it, and it plays a quiet but critical role in how these ecosystems interact with climate. In semi-arid shrublands, the open ground between plants is frequently covered by biological soil crusts: thin mats of cyanobacteria, mosses, and lichens that glue soil particles together. These crusts improve soil moisture and help regulate how water infiltrates the ground versus running off. In shrublands of the American Southwest, well-developed crusts stabilize soils, regulate moisture and infiltration in the bare interspaces between shrubs, and enrich nitrogen and phosphorus pools, with lichen-dominated crusts having a particularly strong effect on soil nutrient levels.15Functional Ecology. Linking biological soil crust attributes to the multifunctionality of vegetated patches and interspaces in a semiarid shrubland
Disturbance of these crusts, whether from trampling by livestock, off-road vehicles, or repeated fire, can expose bare mineral soil that is vulnerable to erosion by wind and water. Once the crust is gone, recovery is measured in decades, not years. For arid shrublands where rainfall is already scarce, losing the biological crust means losing the system’s ability to capture and hold the little water it receives. This connection between living soil surfaces and climate resilience is one of the less visible but most practically important features of shrubland ecosystems.
Drought Sensitivity Varies by Species
One misconception about shrublands is that because their plants tolerate drought, they are uniformly resistant to it. In reality, different shrub species respond to drought stress through different physiological pathways, and those differences determine which species survive extreme events and which do not. Research in the western Mediterranean found that during drought-induced dieback, the juniper Juniperus phoenicea was most negatively affected by rising atmospheric dryness, while oak species responded primarily to declines in soil moisture.16Science of The Total Environment. Declines in canopy greenness and tree growth are caused by combined climate extremes during drought-induced dieback In other words, two common shrubland species standing side by side can be vulnerable to different aspects of the same drought.
This matters because climate change is not simply making things drier. It is shifting the balance between soil moisture depletion, atmospheric dryness, and heat waves in ways that are hard to predict. A shrubland that survived a century of intermittent droughts may lose key species if the character of drought shifts from soil-moisture-driven to atmosphere-driven, or vice versa. Predicting which shrublands are resilient and which are vulnerable requires knowing the physiological strategy of each dominant species, not just the total rainfall.
Shrub Encroachment and the Shifting Boundary With Grasslands
Shrublands do not always stay where they are. Over the past century, many grasslands around the world have been colonized by woody shrubs, a process called shrub encroachment. The causes are debated but likely include a combination of overgrazing (which weakens grasses and frees up space), fire suppression (which removes a key check on woody plants), and rising atmospheric carbon dioxide (which may favor woody species over grasses). The result is that the boundary between grassland and shrubland has been shifting in many regions.
Long-term data from South Africa’s Karoo illustrate how this process plays out unevenly over time. Transects tracked from 1961 to 2012 showed three distinct phases: shrub expansion at about 0.7% per year from 1961 to 1991, a decline at roughly 2.3% per year during the 1990s, and then stabilization at around 22 to 25% woody cover from 1998 onward. Over the full 51-year record, the net change was modest. Broader satellite assessments confirmed that shrub cover remained relatively stable in recent decades regardless of grazing regime, except at the lowest, hottest elevations where succulents were proliferating.17PubMed Central. Shrub encroachment into grasslands: end of an era? The finding challenges the assumption that shrub encroachment is always a one-way ratchet. It can stall, reverse, and restabilize, depending on climatic shifts and local conditions.
Paleoenvironmental Roots
Mediterranean-type shrublands look like products of their current climate, but their evolutionary history is far deeper than the seasonal drought patterns that exist today. Sclerophyll vegetation structurally similar to modern Mediterranean shrublands was already present on nutrient-poor soils during the Cretaceous period, when the climate was wetter and warmer than anything these regions experience now. Fire-adapted plant lineages in southwestern Australia and the Cape Region trace back to the Paleogene, tens of millions of years before the modern Mediterranean climate regime appeared in the middle Miocene.2Annual Review of Ecology, Evolution, and Systematics. Mediterranean Biomes: Evolution of Their Vegetation, Floras, and Climate
This means the tough, small-leaved, fire-resilient shrubs that define these landscapes did not evolve as a response to dry summers. They evolved in response to impoverished soils and fire, and then the arrival of a Mediterranean-type climate created conditions where those pre-adapted lineages could diversify and dominate. The dry-summer climate is a relatively recent overlay on a much older ecological story. It is a useful reminder that the relationship between shrubland vegetation and climate runs in both directions: climate shapes which plants persist, but the evolutionary history of the flora shapes what a particular climate zone ends up looking like on the ground.
What Climate Change Means for Shrublands Globally
Shrublands face a complicated future. A global analysis of potential regime shifts among shrubland, grassland, and forest projected that future climate change would increase the risk of shrubland degradation worldwide, alongside heightened forest loss in Africa and Europe.18Global and Planetary Change. Global potential for regime shifts among shrubland, grassland, and forest “Degradation” in this context can mean different things in different places: conversion to bare ground in arid zones where rainfall drops below the threshold plants need, or invasion by non-native grasses that outcompete native shrubs and alter fire regimes. In the Great Basin, for instance, cheatgrass invasion has transformed vast areas of sagebrush steppe into annual grassland that burns far more frequently than the shrubs can tolerate.
Meanwhile, in the Arctic, warming is expanding shrubland into territory that was historically too cold for woody plants. The net global area of shrubland may not shrink, but its geography is shifting poleward and upslope. For biodiversity, this is not a neutral exchange. The species that depend on sagebrush steppe are different from the species that depend on Arctic tundra, and neither benefits from the other’s expansion or contraction. The climate characteristics that define each type of shrubland are in flux, and the vegetation is responding at its own pace, sometimes keeping up with the climate, sometimes lagging behind, and sometimes being pushed past thresholds from which recovery is unlikely.