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Ecotone

An ecotone is a transition zone between two adjacent ecological communities or biomes, such as a forest and grassland, featuring a blend of species and environmental traits from both while often supporting unique organisms not dominant in either flanking area.^[1] These zones can vary in width from narrow edges to broad belts and are defined by steep gradients in vegetation, climate, or other environmental factors.^[2] Ecotones exhibit distinct properties due to the "edge effect," where influences from adjacent ecosystems create heightened interactions, such as increased nutrient flow and energy exchange.^[2] They frequently display greater species richness and organism density compared to the surrounding habitats, making them hotspots for biodiversity.^[1] For instance, riparian ecotones—linear boundaries along water bodies—can support up to 375% higher plant biomass and over 1,000% greater bird densities than nearby uplands, owing to their high edge-to-area ratios and diverse niches.^[2] Ecologically, ecotones play critical roles as dynamic interfaces sensitive to environmental changes, serving as indicators of broader ecosystem shifts like climate variability or habitat fragmentation.^[3] They facilitate migration corridors for wildlife, enhance ecosystem services such as water purification through processes like denitrification, and act as buffers against disturbances.^[2] In landscapes worldwide, prominent examples include salt marsh-mangrove boundaries in coastal regions and forest-steppe transitions in mountainous areas, where these zones underscore the interconnectedness of biomes.^[4]

Fundamentals

Definition

An ecotone is a transitional zone between two adjacent ecological communities, biomes, or ecosystems, where the characteristics of both merge, often resulting in a heterogeneous mixture of species from the flanking habitats.^[5] This boundary area typically occurs along environmental gradients, such as changes in soil type, moisture, or elevation, and can exhibit either abrupt shifts or more gradual transitions in community composition.^[6] The intermingling of flora and fauna in ecotones frequently leads to unique biotic assemblages that may include species not dominant in either adjacent community, contributing to elevated levels of biodiversity in these zones.^[7] The term "ecotone" was first coined by plant ecologist Frederic E. Clements in 1905, deriving from the Greek words oikos (household or home) and tonos (tension), to describe a "junction zone between two communities or zones of vegetation, characterized by a mixture of the plants of the two sides."^[8] This foundational definition emphasized the dynamic tension at interfaces where ecological processes intensify, such as competition, dispersal, and adaptation.^[6] Ecotones thus represent not merely passive boundaries but active interaction zones influenced by both abiotic and biotic factors, potentially amplifying phenomena like edge effects, where altered microclimates and resource availability affect species distributions.^[9] In ecological theory, ecotones are positioned as critical components of landscape heterogeneity, serving as indicators of environmental change due to their sensitivity to perturbations along gradients.^[7] Their boundaries may be sharp, as in the transition between desert and grassland, or diffuse, spanning wider areas in response to subtle climatic variations, highlighting the spectrum of transitional forms in natural systems.^[6] This variability underscores the ecotone's role as a conceptual bridge between discrete habitat patches, fostering evolutionary and ecological processes at the interface.^[8]

Etymology

The term "ecotone" derives from the Greek roots oikos, meaning "house" or "habitat," and tonos, meaning "tension" or "strain," thus denoting a zone of tension between distinct habitats or ecological communities.^[10] This etymological construction emphasizes the transitional nature of such areas, where adjacent ecosystems exert mutual influences, creating a dynamic boundary rather than a static divide.^[5] The term was first coined in 1905 by American botanist and ecologist Frederic E. Clements, who introduced it in his work on plant succession and community structure as a more precise descriptor for what had previously been termed a "tension zone." Clements proposed "ecotone" to capture the ecological stress and intermingling at habitat interfaces, building on earlier observations of vegetation transitions.^[11] Throughout the 20th century, the term gained prominence in ecological literature, appearing in seminal texts on biogeography and community ecology, where it evolved from a botanical concept to a broader framework applicable to diverse biomes and environmental gradients.^[12] A related term, "ecocline," emerged later to describe gradual environmental transitions without sharp boundaries, coined by ecologist Robert H. Whittaker in 1960 to denote continuous gradients in community composition along ecological factors like climate or soil.^[13] This distinction highlights ecotones as abrupt interfaces, while ecoclines represent smoother, clinal variations, enriching the vocabulary for analyzing habitat shifts in ecology.^[14]

Characteristics

Structural Features

Ecotones are characterized by the intergradation of dominant species from adjacent biomes, where vegetation and faunal assemblages blend, often resulting in a mosaic of plant forms that reflect influences from both sides of the transition. This mixing can lead to the presence of hybrid species or unique genotypes adapted specifically to the boundary conditions, such as increased genetic diversity in peripheral populations along ecotonal gradients. For instance, in arid-semiarid transitions like those in Israel, bird species exhibit higher morphological variation and rare alleles due to the convergence of Mediterranean and desert communities.^[9] The width and sharpness of ecotones vary significantly, ranging from narrow zones spanning mere meters—such as abrupt beach-to-dune transitions driven by salt spray gradients—to broad bands extending kilometers, like the forest-tundra ecotone in Quebec, which can reach up to 300 km in extent. This variability is primarily influenced by the steepness of the underlying environmental gradient; steeper gradients, such as those on volcanic lava flows in Hawaii, produce sharper ecotones with more defined boundaries, while gentler slopes allow for wider transitional areas.^[9]^[15] Microhabitats within ecotones often feature distinct soil properties, moisture regimes, and light availability that differ from the core biomes, supporting specialized communities not found elsewhere. For example, in wetland-woodland ecotones, steep gradients in soil depth and moisture create pockets of unique hydrologic conditions that foster rare plant assemblages adapted to fluctuating water levels. Similarly, forest-open habitat ecotones harbor varied microclimatic regimes, including shaded understories and exposed edges, which promote diverse insect and plant guilds responsive to these localized variations.^[9]^[16]^[17]

Edge Effects

Edge effects describe the heightened influence of adjacent ecosystems on the boundary zone of an ecotone, resulting in modified environmental conditions and ecological interactions that extend into the transition area. These effects arise from the abrupt juxtaposition of contrasting habitats, leading to changes in resource availability, microclimates, and biotic pressures such as predation or competition. Unlike uniform interior environments, ecotones experience amplified gradients that can alter species distributions and community dynamics across depths ranging from tens to hundreds of meters.^[18] Key impacts include abiotic alterations like increased light penetration at the edge, which elevates understory illumination by up to 2.5 times compared to forest interiors, and consequent temperature fluctuations of 2–5°C higher during the day due to reduced canopy cover. These microclimatic shifts also promote elevated herbivory, as generalist herbivores exploit the more open conditions and diverse forage, with studies documenting 20–50% higher damage rates on edge vegetation than in core areas. Additionally, edge effects facilitate invasive species ingress by providing disturbed, resource-rich zones with lower competitive resistance, enabling non-native plants to establish and spread into adjacent habitats. Biotic responses often manifest as increased biodiversity, with quantitative studies reporting up to a doubling of species richness in ecotone zones relative to surrounding ecosystems, though this varies by habitat contrast and taxon.^[19]^[20]^[21]^[22] Temporal dynamics of edge effects distinguish short-term responses, such as immediate post-disturbance surges in light and temperature following events like logging, from long-term patterns where effects may deepen or stabilize over decades. Short-term effects typically intensify biotic interactions like predation within the first few years, while long-term dynamics can lead to persistent structural changes, including gradual shifts in species composition as invasive species become entrenched or native communities adapt. These variations underscore the need to consider time scales in assessing ecotone functionality, as initial enhancements in resource availability may evolve into chronic stressors over extended periods.^[18]^[23]

Formation and Dynamics

Environmental Processes

Ecotones form where environmental variables such as temperature, precipitation, and soil pH exhibit rapid spatial changes, resulting in tension zones between adjacent ecosystems.^[24] This gradient theory posits that ecotones emerge as transitional boundaries along continuous environmental gradients, where the rate of change in abiotic conditions exceeds the tolerance limits of dominant community types, leading to abrupt shifts in species composition.^[25] In these zones, the interplay of multiple gradients amplifies the sharpness of the transition, creating a narrow band of heightened environmental variability that maintains the ecotone's distinct character.^[9] Key abiotic processes driving ecotone creation and maintenance include climate shifts, which alter thermal and moisture regimes over time and space, often compressing or expanding ecotones as global or regional patterns evolve.^[24] Topography plays a critical role through elevational gradients, where changes in altitude produce steep variations in temperature, wind exposure, and solar radiation, as seen in montane treeline ecotones where forest gives way to alpine tundra over short vertical distances.^[26] Hydrological processes, particularly in riparian zones, contribute via fluctuating water levels and nutrient flows in river floodplains, where periodic inundation creates salinity and moisture gradients that delineate wetland from terrestrial communities.^[27] Additionally, disturbances such as fire and erosion reinforce ecotone boundaries by resetting successional trajectories and exposing underlying soil variations; for instance, recurrent fires in savanna-forest interfaces prevent encroachment by woody species, while erosional forces in lotic systems sculpt sharp transitions between aquatic and terrestrial habitats.^[28]^[29] Modeling approaches for understanding these processes rely on conceptual gradient analysis, which maps vegetation patterns against measured environmental variables to identify zones of rapid compositional turnover without invoking mathematical derivations.^[25] This method, pioneered in ecological studies, treats ecotones as inflection points along ordination axes representing composite gradients, allowing researchers to predict ecotone stability based on the steepness and directionality of abiotic drivers. Such analyses highlight how abiotic gradients interact with biotic responses to sustain ecotones as dynamic features of landscapes.^[24]

Biotic Influences

Biotic influences play a crucial role in shaping ecotones by mediating species interactions that determine the sharpness and position of ecological boundaries. Competition among species with differing environmental optima can create discrete zones within ecotones, while facilitation occurs when species modify the environment to benefit others with similar tolerances. Predation, exemplified by rodent consumption of seeds, can limit recruitment and reinforce boundary transitions, as observed in alpine treeline ecotones where seed predation rates decline with elevation, affecting Swiss stone pine (Pinus cembra) establishment. Keystone species, often acting as ecosystem engineers, stabilize these transitions; for instance, beavers (Castor canadensis) alter hydrology through dam-building, creating wetland-forest interfaces that persist despite abiotic pressures. Dispersal and migration of organisms across ecotones significantly influence community assembly and boundary dynamics. Seed dispersal by animals, such as spotted nutcrackers (Nucifraga caryocatactes), concentrates propagules at optimal sites within ecotones, driving recruitment patterns more than abiotic factors in elevational limits; in the Swiss Alps, nutcracker caches peaked at intermediate elevations, facilitating pine establishment beyond dispersal limits. Animal migration can similarly transport nutrients or predators, blurring or sharpening boundaries, though high dispersal rates may homogenize communities if not counteracted by local interactions. Feedback loops involving vegetation reinforce ecotone persistence by modifying local conditions. Plants alter microclimates and soils through canopy shading and transpiration, creating self-sustaining zones; in woodland-grassland ecotones, tree establishment reduces wind speeds and increases humidity, promoting further colonization. Root systems exemplify this by enhancing soil stability and nutrient retention, preventing biome shifts; in arid ecotones, deep roots access water and modify infiltration, sustaining vegetation patches against expansion of neighboring biomes. These biotic feedbacks complement environmental processes in maintaining ecotone structure.

Ecotones versus Ecoclines

An ecotone represents a discrete transition zone between two adjacent ecological communities or biomes, characterized by a relatively sharp boundary where species assemblages change abruptly.^[30] In contrast, an ecocline describes a continuous gradient of species replacement along an environmental axis, such as soil moisture or temperature, resulting in a smooth, gradual shift in community composition without a distinct edge.^[31] These definitions highlight the fundamental difference in spatial structure: ecotones often manifest as narrow zones influenced by abrupt environmental discontinuities, while ecoclines extend over broader areas with incremental variations.^[32] Ecotones tend to form sharper boundaries due to physical or biological barriers that restrict species dispersal or survival, such as steep elevation changes or soil discontinuities, whereas ecoclines develop in more uniform environments where species respond individualistically to subtle gradients.^[30] This distinction has roots in early 20th-century ecological debates, notably between Frederic Clements, who viewed vegetation as discrete, integrated units separated by clear ecotones akin to organismal boundaries, and Henry Gleason, who advocated a continuum hypothesis emphasizing gradual, individualistic species responses that align with ecoclines.^[33] Clements's superorganism model supported the existence of well-defined ecotones as evidence of community cohesion, while Gleason's perspective challenged this by highlighting the rarity of truly sharp transitions in favor of fluid ecoclines driven by environmental heterogeneity.^[30] Empirical studies have largely supported Gleason's continuum view, though ecotones persist in contexts with strong barriers.^[33] In practice, ecological transitions exist on a spectrum, with many ecotones embedding internal ecoclines where fine-scale gradients occur within the broader boundary zone.^[31] For instance, what appears as a single ecotone may encompass overlapping ecoclines along multiple environmental axes, blurring the binary distinction and reflecting underlying formation processes like gradual resource availability shifts.^[32] This nested structure underscores the conceptual overlap, as both concepts arise from similar environmental gradients but differ primarily in the rate and detectability of change.^[31]

Types of Ecotones

Ecotones are classified according to various schemes that emphasize their scale, origin, and sharpness, providing a framework for understanding their ecological roles. At the scale level, ecotones range from micro-ecotones, such as transitions within soil layers or microbial communities on the order of micrometers, to macro-ecotones spanning large biomes over kilometers, influencing patterns from local habitats to global distributions.^[34] This variation in extent affects the intensity of edge effects and biodiversity dynamics across ecosystems.^[35] Regarding origin, ecotones are categorized as natural or anthropogenic; natural ecotones arise from endogenous or exogenous environmental processes within ecosystems, while anthropogenic ones result from human activities like land clearing or urbanization, often creating artificial boundaries with distinct community responses.^[36] Sharpness further delineates ecotones into tension zones, which are abrupt transitions driven by species interactions and environmental stress leading to high instability and potential for rapid shifts, versus diffuse ecotones that exhibit gradual changes over broader areas with less pronounced boundaries.^[37]^[38] Key subtypes include zonal ecotones, primarily driven by macroclimatic factors such as temperature and precipitation gradients that align vegetation with broad climatic zones; azonal ecotones, influenced by local disturbances like fire or flooding that deviate from climatic patterns; and physiographic ecotones, shaped by topographic features including elevation, slope, and landforms that alter local microclimates and soil conditions.^[39] Recent classifications post-2000 have incorporated urban ecotones as a prominent anthropogenic subtype, recognizing their role in modified landscapes where city edges blend natural and built environments, often amplifying biodiversity through novel interactions.^[40] In contrast to ecoclines, which represent continuous gradients without distinct boundaries, ecotones typically feature more defined transitions that can vary in sharpness.^[36]

Ecological Role

Biodiversity Patterns

Ecotones frequently exhibit elevated beta diversity compared to adjacent homogeneous habitats, driven by pronounced species turnover as environmental conditions transition abruptly. This turnover arises from the replacement of species adapted to one biome with those suited to another, resulting in high compositional dissimilarity across short distances. For instance, in mountain-ecotone systems, beta diversity is enhanced by landscape heterogeneity, leading to distinct community assemblages that differ markedly from surrounding plains.^[41] Similarly, analyses of patch edges confirm higher β-diversity values in transition zones, underscoring their role in facilitating species replacement.^[42] Alpha diversity in ecotones can peak due to increased habitat heterogeneity, which provides a mosaic of microhabitats supporting a broader range of species. Local species richness is often higher in these zones than in core areas of adjacent biomes, as the varied conditions allow for the coexistence of taxa from multiple pools. Studies in mountain and ecotone sites demonstrate comparatively elevated alpha diversity, attributed to this structural complexity.^[41] Edge effects contribute to this pattern by amplifying resource availability and niche opportunities at boundaries.^[22] The overlap of species pools from neighboring ecosystems further boosts overall diversity in ecotones, enabling the presence of both shared and unique taxa that may not thrive in uniform habitats. This overlap can result in substantially higher species richness, with some ecotonal configurations yielding up to twice the number of species compared to adjacent areas through enhanced habitat feathering and light heterogeneity.^[22] Meta-analyses and reviews indicate that such patterns are context-dependent but consistently highlight ecotones as potential hotspots.^[42] Recent research emphasizes ecotones as reservoirs of genetic diversity, particularly under climate change pressures, where hybrid zones and gene flow between biomes foster adaptive variation. In Neotropical forest ecotones, such as those between Cerrado and Atlantic rainforests, these transitions host hotspots of genetic exchange that buffer against environmental shifts.^[43] This role positions ecotones as critical for maintaining intraspecific variation, supporting speciation and resilience as climates warm and habitats shift.^[44]

Ecosystem Stability

Ecotones contribute to ecosystem stability by serving as buffers that mitigate the propagation of disturbances across biomes, thereby enhancing overall resilience to environmental changes. Their heterogeneous structure and elevated biodiversity enable them to absorb shocks from invasions or climatic shifts, preventing rapid encroachment into adjacent ecosystems. For example, the diverse functional traits in ecotone communities stabilize key processes like primary production and decomposition, reducing vulnerability to perturbations.^[45] Ecotones also function as early warning zones for impending biome shifts, where subtle changes in species composition or physiological stress signal broader ecosystem transitions before they affect entire biomes. In Neotropical forest ecotones, monitoring responses to precipitation gradients has revealed non-linear shifts that forecast drought-induced instability, allowing for proactive assessment of resilience. This role has gained prominence in post-2010s climate research, where ecotones are modeled as sentinels for tipping points in global stability frameworks.^[45]^[46] The dynamics of ecotones often involve hysteresis, a phenomenon where ecosystems persist in alternative stable states after a disturbance, complicating recovery and influencing long-term stability. In coastal ecotones, microclimate feedbacks—such as canopy-induced warming—can trigger irreversible transitions to woody dominance, with thresholds around -7°C marking critical shifts. Generalized models of ecosystem hysteresis identify bistable hotspots in evergreen-deciduous forest ecotones, driven by soil-related feedbacks that amplify resistance to reversal.^[47]^[48] Ecotones further bolster stability through their influence on nutrient cycling at boundaries, where intensified exchanges of elements like nitrogen and phosphorus sustain adjacent ecosystems. In land-water ecotones, microbial communities mediate biogeochemical transformations, promoting nutrient retention and reducing losses that could destabilize productivity. From a soil perspective, ecotone dynamics regulate nutrient availability via organic matter decomposition and cation exchange, enhancing the resilience of transitional zones to fluctuations.^[49]

Examples

Terrestrial Transitions

Forest-grassland ecotones represent dynamic transition zones where woody vegetation gradually gives way to open grassy landscapes, often driven by gradients in precipitation, fire regimes, and soil fertility. In African savannas, such as those in the Serengeti or Tsavo regions, these ecotones feature scattered trees like Acacia tortilis and Acacia drepanolobium that facilitate understory grasses while competing for resources, creating a mosaic of tree-grass interactions that enhance biodiversity.^[50] Fire plays a pivotal role in maintaining these boundaries, suppressing tree establishment in grass-dominated areas while allowing acacia species to regenerate in less frequently burned zones, resulting in abrupt shifts over short distances.^[51] Herbivory by large mammals further shapes the ecotone, as selective browsing on seedlings influences tree density and promotes grass persistence.^[52] Desert-shrubland boundaries exemplify sharp ecotones formed by steep aridity gradients, where vegetation abruptly transitions from sparse desert flora to denser shrub communities. In the fringes of the Sonoran Desert, encompassing parts of Arizona and Sonora, Mexico, this ecotone is marked by a shift from cactus-dominated landscapes, such as saguaro and cholla, to semi-desert shrublands with creosote bush (Larrea tridentata) and mesquite, driven by annual precipitation increasing from under 200 mm to over 300 mm.^[53] These transitions occur over elevations from 300 to 1,000 meters, with aridity limiting shrub establishment in the core desert while enabling proliferation at the edges through slightly higher moisture and cooler microclimates.^[54] Climate variability exacerbates these shifts, as prolonged droughts favor desert expansion into shrublands, altering soil moisture and nutrient cycling.^[54] Altitudinal treelines form elevational ecotones where forests yield to alpine meadows, primarily controlled by decreasing temperatures with height. In the European Alps, such as in the Valais region of Switzerland, the treeline typically occurs between 1,850 and 2,200 meters above sea level, dominated by larch (Larix decidua) and stone pine (Pinus cembra) that tolerate cold but are limited by isotherms where growing season temperatures exceed 5°C for at least 100 days. Temperature gradients of about 0.6°C per 100 meters drive this transition, creating a band of krummholz—dwarfed, wind-sculpted trees—before open tundra. In the western Italian Alps, recent warming has caused upward advances of up to 115 meters over the 20th century (1901–2000).^[55] Geomorphological features like rocky slopes further define the ecotone by providing microsites for seedling survival amid harsh winds and short growing seasons.^[56] Edge effects in these treelines, such as increased light penetration and wind exposure, often boost understory diversity but heighten vulnerability to disturbance.^[56]

Aquatic and Marine Boundaries

Aquatic and marine ecotones represent dynamic transition zones where freshwater and saltwater systems interface with adjacent habitats, fostering unique ecological interactions distinct from terrestrial boundaries. River-lake interfaces exemplify these, with riparian zones serving as ecotones that blend aquatic and terrestrial influences through periodic flooding and moisture gradients.^[57] These zones feature vegetation adapted to saturated soils, such as willows and sedges, which stabilize banks and facilitate nutrient exchange between water bodies and surrounding land.^[58] In lake ecosystems, enhanced riparian cover in these ecotones boosts functions like organic matter retention and sediment trapping, supporting higher microbial and invertebrate diversity at the interface.^[59] Such formation processes, driven by hydrological connectivity, underscore the role of water flow in shaping these boundaries.^[60] Estuaries form prominent saltwater-freshwater ecotones, where river outflows mix with tidal marine waters, creating salinity gradients that drive habitat zonation and species adaptations.^[61] These areas often support dense stands of salt-tolerant vegetation, including salt marshes dominated by cordgrass (Spartina spp.) and, in subtropical regions, mangroves like black mangrove (Avicennia germinans), which trap sediments and buffer against wave energy.^[62] The Chesapeake Bay illustrates this transition vividly, encompassing over 1,000 km² of tidal wetlands that sustain exceptional biodiversity, including migratory fish, birds, and crustaceans reliant on the fluctuating salinity for reproduction and foraging.^[63] This ecotone's productivity stems from nutrient inputs from upstream rivers, making it a critical nursery for commercially important species like blue crabs.^[64] In marine settings, coral reef-lagoon ecotones arise along depth and hydrodynamic gradients, marking shifts from exposed reef crests to sheltered lagoon interiors, where light penetration and water motion alter community composition.^[65] These transitions often exhibit heightened biodiversity due to overlapping assemblages, with reef-front corals like branching Acropora giving way to lagoonal seagrasses and foraminifera in shallower, calmer waters.^[66] For instance, along the Kenyan coast, ecotonal zones between fringing reefs and lagoons show non-linear patterns of coral diversity, peaking at boundaries where depth increases from 1-5 meters promote hybrid communities resilient to localized disturbances.^[67] Such depth-driven changes influence trophic structures, with herbivorous fish and algae dominating lagoon sides compared to predatory fish on outer reefs.^[68] Recent studies from the 2020s emphasize ocean acidification's underappreciated impacts on these marine ecotones, accelerating shifts in community dynamics through reduced carbonate availability. In coral reef-lagoon systems, acidification lowers aragonite saturation states (often below 3.5 in surface waters), impairing coral calcification and favoring dissolution of reef frameworks, which narrows ecotonal habitats and diminishes biodiversity hotspots.^[69] Estuarine ecotones face compounded effects, as acidification exacerbates shellfish mortality—such as oysters in Chesapeake Bay—and alters salinity-tolerant microbial communities, potentially compressing marsh-mangrove transitions.^[70] Observations from Florida reefs indicate partial buffering by seagrass-lagoon interactions, yet overall, these changes threaten the structural integrity of ecotones, with projected 20–60% declines in coral calcification rates by mid-century under high-emission scenarios (as of ~560 ppm pCO₂).^[71]

Human Interactions

Anthropogenic Impacts

Human activities have profoundly altered ecotones through habitat fragmentation, primarily via deforestation and land-use conversion, which generate artificial edges and amplify edge effects such as altered microclimates, increased predation, and invasive species penetration. In tropical forests, a 2021 analysis revealed that the proportion of forest edge area rose from 27% to 31% of total forest cover between 2000 and 2010, with the sharpest increases occurring in Africa due to accelerated fragmentation. More recent 2024 research estimates that degradation from these edge effects in tropical moist forests is 200% greater than prior models suggested, resulting in substantial declines in aboveground biomass extending 500 meters or more into intact forest interiors. Climate change exacerbates these alterations by shifting ecotones poleward or upslope, hastening biome transitions and challenging species adapted to stable boundaries. In the Arctic, warming has driven the tundra-forest ecotone northward, with shrubs and trees encroaching into tundra habitats; a 2024 NASA study projects this greening trend to intensify through 2100, with positive structural changes expected in over 1.3 million square kilometers of transitional tundra-forest areas in North America, leading to taller, greener vegetation.^[72] Similarly, a 2022 investigation confirmed boreal forest expansion into alpine and arctic tundra, with tree lines advancing in response to rising temperatures.^[73] Agricultural pollution, especially nutrient runoff from fertilizers, induces eutrophication in aquatic systems, which erodes the distinctiveness of ecotones by promoting excessive algal growth and hypoxic conditions that displace native riparian and wetland vegetation. This nutrient overload blurs transitions between lotic and lentic waters or aquatic-terrestrial interfaces, reducing habitat heterogeneity.^[74] Eutrophication also enhances the spread of invasive species, as nutrient-rich environments favor opportunistic non-natives; for example, a 2024 study demonstrated that invasive submerged macrophytes, thriving under eutrophic conditions, heighten the vulnerability of native aquatic plants in transitional zones.^[75] Urban expansion in the 2020s has intensified these pressures by encroaching on ecotone margins, converting natural transitional habitats into impervious surfaces and fragmenting remaining edges. A 2022 global assessment projected that urban growth could drive habitat loss affecting over 800 vertebrate species, with ecotones particularly vulnerable due to their role as biodiversity hotspots, leading to local species richness declines of up to 50% in urban-adjacent areas.^[76] Emerging 2020s research further identifies microplastics as a novel threat to ecotones, where these particles accumulate in sediment and soil at land-water interfaces, disrupting microbial communities, nutrient cycling, and invertebrate assemblages in both terrestrial and aquatic transitions.^[77]

Conservation Approaches

Conservation approaches for ecotones emphasize proactive protection and restoration to mitigate threats from habitat fragmentation and land-use changes. Buffer zones are a primary method, establishing vegetated strips around ecotone boundaries to reduce external pressures such as nutrient runoff and erosion, as seen in Australian coastal programs protecting mangrove and saltmarsh transitions against climate impacts.^[78] Restoration efforts often involve reforestation to reconnect fragmented zones and targeted removal of invasive species, which can alter native community structures; for instance, manual pulling and herbicide application in southeastern U.S. granite outcrop ecotones aimed to recover native plant richness, though results highlighted the need for long-term monitoring due to slow recovery dynamics.^[79] These methods enhance ecotone resilience by preserving transitional habitats that support species adaptation. Policy frameworks integrate ecotones into broader protected area networks, such as UNESCO's Man and the Biosphere Programme, where buffer and transition zones within biosphere reserves facilitate sustainable management of ecosystem boundaries, promoting biodiversity conservation alongside human activities across more than 130 countries (as of 2025).^[80] In 2025, UNESCO designated 26 new biosphere reserves across 21 countries, many incorporating ecotone buffer zones to bolster resilience against ongoing environmental pressures.^[81] Monitoring relies on remote sensing technologies, including satellite imagery and probabilistic modeling, to map ecotone shifts and vegetation gradients with high accuracy, enabling early detection of degradation in areas like forest-steppe boundaries. Such tools support adaptive management by quantifying changes in ecotone extent over time. Challenges in ecotone conservation include adapting to climate-induced species migrations, where shifting timberlines, as observed in the Andes over four decades, act as barriers to upslope movement, necessitating corridor restoration to facilitate dispersal. Innovations in the 2020s incorporate community-based management, prioritizing ecotones rich in endemic species for local stewardship initiatives that align conservation with cultural practices, as proposed for vegetation transitions in biodiversity hotspots. Emerging AI-driven approaches, leveraging deep learning on satellite data, enhance ecotone mapping post-2020 by predicting dynamic boundaries and informing targeted interventions, addressing gaps in traditional surveys.

References

[1]
[PDF] THE ECOTONE - University of Oregon
ECOTONE: A transition zone between two adjacent communities, such as a forest or grassland. It has some of the characteristics of each bordering community ...
[2]
[PDF] Riparian Zones—The Ultimate Ecotones? - USDA Forest Service
A modern definition of ecotone refers to areas of steep vegetation gradients ... ecological principle of ecotones. Riparian zones have large energy ...
[3]
[PDF] 1 Climate change drives increased directional movement ... - NSF PAR
Ecotones are boundary zones formed where overlap between neighboring ecosystems creates an. 21 intermediate ecosystem with unique ecological characteristics.
[4]
Dynamics of mangrove-marsh ecotones in subtropical coastal ...
Apr 1, 2013 · Ecotones are areas of sharp environmental gradients between two or more homogeneous vegetation types. They are a dynamic aspect of all ...
[5]
Ecotone - an overview | ScienceDirect Topics
Ecotones are areas of steep transition between ecological communities, ecosystems, or regions, where the environment rapidly shifts from one type to another.
[6]
Ecotones in vegetation ecology: methodologies and definitions ...
Feb 28, 2009 · (1991), an ecotone can be defined as: “An environmentally stochastic interaction zone between ecological systems with characteristics defined in ...
[7]
The Role of Ecotones in Emerging Infectious Diseases - PMC
Ecotones, the edges or transition zones between two adjacent ecological systems are frequently mentioned in the zoonotic and vector-borne disease literature.
[8]
[PDF] Proceedings: shrubland ecotones - USDA Forest Service
... Ecotones. Ecotone Definition. Pioneering American plant ecologist Frederic Clements. (1905) defined an ecotone as a “junction zone ...
[9]
Ecotone - an overview | ScienceDirect Topics
The origin of the word “ecotone” is in the Greek roots “oikos” (home) and “tonus” (tension). Many different definitions and terms have been used in the ...<|control11|><|separator|>
[10]
Ecotone Explained - Ecological Society of America
An ecotone is a border zone where ecological systems meet, sometimes forming a new community, and the transition from one ecosystem to another.
[11]
(PDF) Ecotones: Introduction, Scale, and Big Sagebrush Example
This "zone of tension" between biological societies is called ecotone ( Clements, 1905 ;Livingston, 1903 ). Within ecotones, biological diversity and ...Missing: coined | Show results with:coined
[12]
https://www.sciencedirect.com/science/article/pii/S0306987725002488
[13]
Ecotones and Ecoclines Are Different - jstor
b) the concept of ecocline (coined independently by. Whittaker 1960 and, as coenocline, by van der Maarel &. Westhoff 1964), a gradient zone which is ...
[14]
ecocline - Wiktionary, the free dictionary
Etymology. From eco- +‎ -cline. Noun. ecocline (plural ecoclines). A gradation from one ecosystem to another when there is no sharp boundary between the two ...
[15]
A global framework for linking alpine‐treeline ecotone patterns to ...
Nov 9, 2020 · 3), steep slopes are likely to have narrower ecotones than gentle slopes. Of course, the ecotone width should thus be interpreted with respect ...Missing: sharpness steepness
[16]
Ecotones as indicators: boundary properties in wetland-woodland ...
Dec 30, 2015 · Well-defined ecotones were associated with steep gradients in soil depth and soil moisture. Most ecotones showed a change in vegetation from ...Ecotones As Indicators... · Article Pdf · Explore Related SubjectsMissing: specialized | Show results with:specialized
[17]
Interspecific differences in microhabitat use expose insects to ...
Dec 9, 2022 · Ecotones linking open and forested habitats contain multiple microhabitats with varying vegetal structures and microclimatic regimes.
[18]
Edge effects in fragmented forests: implications for conservation
Edges are presumed to have deleterious consequences for the organisms that remain in forest fragments. However, there is substantial discrepancy among ...
[19]
[PDF] Hansen et al. Edge effects across ecosystem types
Feb 25, 2008 · Moreover, studies of edge effects in nonforest vegetation types are fewer and estimates of AGB are more difficult to obtain. The analysis of ...Missing: seminal | Show results with:seminal
[20]
Plant Herbivore Interactions at the Forest Edge - ResearchGate
Key conclusions are that herbivores, especially generalists, profoundly benefit from forest edges, often due to favourable microenvironmental conditions.
[21]
Edge effects of an invasive species across a natural ecological ...
Aug 6, 2025 · Natural habitats adjacent to human-modified areas often suffer edge effects stemming from physical disturbance, elevated predator densities, ...
[22]
Edge Feathering Across Forest-Meadow Ecotones Increases Light ...
Edge feathering increased light heterogeneity by more than 2.5-fold. It also significantly increased biodiversity, yielding twice the species richness.
[23]
A unifying framework for understanding how edge effects reshape ...
Aug 13, 2025 · These studies are typically short-term and focus on one site or forest ecosystem type. Long-term experiments, such as the Biological Dynamics ...
[24]
(PDF) Ecotones and Ecological Gradients - ResearchGate
Jul 19, 2015 · Ecotones are areas of steep transition between ecological communities, ecosystems, or ecological regions along an environmental gradient.Missing: sharpness | Show results with:sharpness
[25]
GRADIENT ANALYSIS OF VEGETATION* - WHITTAKER - 1967
An analysis of a vegetation-microenvironmental complex on prairie slopes in Saskatchewan. Ecol. Monogr. 34, 421–42.Missing: ecotones | Show results with:ecotones
[26]
Global assessment of vegetation patterns along topographic gradients
Sep 19, 2024 · Our mapping reveals clear geographic patterns indicating that topography strongly influences vegetation in arid and polar ecosystems.
[27]
[PDF] Biodiversity of floodplain river ecosystems: ecotones and connectivity1
Hydrological connectivity, the transfer of water between the river channel and the floodplain and between surface and subsurface compartments, has major ...
[28]
Fire enhances the complexity of forest structure in alpine treeline ...
Feb 6, 2018 · Fire causes increased non-forest plots and decreased open/closed forest plots, with higher severity causing greater mortality of larger trees, ...
[29]
[PDF] CHAPTER 5 LANDSCAPE DISTURBANCES AND LOTIC ECOTONES
Direct influences may be viewed as variations in ecotone and landscape configurations from 'normal conditions' for edaphic gradients, hydrologic regimes, and ...Missing: climate | Show results with:climate
[30]
Method and metaphysics in Clements's and Gleason's ecological ...
Clements had argued that natural vegetation tended over time to become organized into discrete units separated by narrow or broad ecotones. These units ...Missing: ecocline | Show results with:ecocline
[31]
Ecotone or Ecocline: Ecological Boundaries in Estuaries
Two main ecological boundaries, ecotone and ecocline, have been defined in landscape ecology. At this scale, the estuary represents a boundary between rivers ...
[32]
Landscape and plant community boundaries in biogeography
The term 'ecotone' has traditionally been used to describe boundaries between plant communities and ecosystems at a range of scales. Various definitions are ...
[33]
[PDF] superorganism Gleason – individualistic Test
Clements – superorganism. Gleason – individualistic. Test: sharp versus gradual boundaries. Few sharp !ecotones" or boundaries between discrete ecosystems.Missing: ecocline | Show results with:ecocline
[34]
A Classification of Ecological Boundaries
We consider four main classes of boundary traits: (1) origin and maintenance, (2) spatial structure, (3) function, and (4) temporal dynamics (see box). These ...
[35]
(PDF) Spatial scale types and measurement of edge effects in ecology
The paper classifies edge effects into three spatial scales: large (biome ecotone), meso (ecological ecotone), and small (community ecotone), each demonstrating ...Missing: origin sharpness
[36]
Evidence on ecotone concepts from switch, environmental and ...
Aug 10, 2025 · Ecotones can be differentiated on the bases of the sharpness of their communities (Lloyd et al., 2000) . The most appropriate causes are; sharp ...
[37]
[PDF] species diversity patterns at ecotones - Faculty
All ecotone characteristics, including species richness, result from the particular ecological condition and processes at the site, as well as properties of the ...
[38]
Ecotone Classification According to its Origin
Weaver (1960) defined ecotone as a transition zone between vegetation types containing abiotic and biotic components. The ecotones in terrestrial systems ...
[39]
[PDF] Ecoregion Mapping and Boundaries
Feb 2, 2006 · Local classes correlate with many of the variations from the zonal pattern and are termed azonal. One ignores these local variations in mapping ...
[40]
(PDF) Effects of Ecotones on Biodiversity - ResearchGate
PDF | On Jan 1, 2017, S. Kark published Effects of Ecotones on Biodiversity | Find, read and cite all the research you need on ResearchGate.
[41]
Mountains and their ecotones increase landscape heterogeneity ...
Dec 7, 2022 · Comparison was made on the local patterns of species richness and evenness (alpha diversity), as well as community turnover (beta diversity) ...
[42]
(PDF) Ecotones: Marginal or Central Areas of Transition?
Aug 6, 2025 · Areas of environmental transition, where ecological communities coincide, are sometimes termed ecotones. These regions often correspond with ...
[43]
Ecotones as Windows into Organismal-to-Biome Scale Responses ...
Aug 27, 2024 · In this review, we describe how studying ecotones can provide key indicators for monitoring the state of Neotropical forests from organisms to ecosystems.
[44]
https://doi.org/10.1002/ece3.8540
[45]
https://doi.org/10.3390/plants13172396
[46]
https://doi.org/10.1111/nph.15145
[47]
https://doi.org/10.1002/ecy.3107
[48]
https://doi.org/10.1038/s41467-024-48676-5
[49]
Editorial: Microbial involvement in biogeochemical cycling ... - Frontiers
Land-water ecotones, such as coastal areas, wetlands, riverine zones, and aquifer recharge regions, are characterized by intensive mass and energy exchanges, ...
[50]
[PDF] Tree - Grass Interactions on an East African Savanna - WUR eDepot
In an East African savanna in Tarangire, I studied what determines whether Acacia tortilis trees interfere or facilitate understorey grass growth and especially ...
[51]
Many shades of green: the dynamic tropical forest–savannah ...
Sep 19, 2016 · The forest-savannah transition is a widespread ecotone separating two productive ecosystems, shaped by water, fire, herbivory, and soil, and is ...
[52]
Framework for Exploring the Determinants of Savanna and ...
Jul 1, 2006 · We propose a new scientific framework for identifying determinants of savanna and grassland distribution, which advocates (a) the recognition ...
[53]
Sonoran Desert Network Ecosystems - National Park Service
May 2, 2023 · Bounded on the north by the Mogollon Rim, the Sonoran Desert grades into the Chihuahuan Desert to the east, the Mohave Desert to the west, and ...Sonoran Desert Network... · Land Use History · Biomes And Subdivisions
[54]
None
Below is a merged summary of the desert-shrubland ecotones in the southwestern US, consolidating all information from the provided segments into a dense and comprehensive response. To maximize detail and clarity, I’ve organized key data into tables where appropriate (in CSV-like format) and included narrative text for contextual and qualitative information. All unique details, projections, examples, and URLs are retained.
[55]
Climate Warming and the Recent Treeline Shift in the European Alps
At the study site, the recent dramatic air temperature increase has caused a treeline upward shift of 115 m over the period 1901–2000. This treeline advance was ...
[56]
Evidence for 40 Years of Treeline Shift in a Central Alpine Valley
Feb 17, 2023 · Alpine treeline ecosystems are generally expected to advance with increasing temperatures and after land-use abandonment.
[57]
1 INTRODUCTION | Riparian Areas: Functions and Strategies for ...
A riparian area is an area of land directly influenced by permanent water. It has visible vegetation or physical characteristics reflective of permanent water ...
[58]
[PDF] Defining stream riparian zones across multidimensional ...
Riparian zones were initially defined as integral parts of freshwater ecosystems (e.g., Hynes, 1975) or as ecotones occupying the transition between ...
[59]
Role of Lake Aquatic–Terrestrial Ecotones in the Ecological ...
Jun 26, 2023 · This paper reviews the recent studies on the restoration ability of eutrophic water bodies in lake aquatic–terrestrial ecotones in recent years.Missing: classifications post-
[60]
Management Considerations for Prescribed Fires in Riparian Zones ...
Sep 16, 2025 · Riparian zones link upland and aquatic habitats. Riparian zones are ecotones, or transition areas, that occur between and connect a body of ...
[61]
[PDF] Estuarine Environments
Transition zones (ecotones) occur between two or more diverse communities or habitats. Species that have highest abundance in ecotones are called “edge species”.
[62]
[PDF] Long-term Monitoring of Estuarine Vegetation Communities
Environmental factors affecting recent summertime eelgrass diebacks in the lower Chesapeake Bay ... Ecotones are transition zones between adjacent ecological ...
[63]
[PDF] Index of Ecological Condition for the Tidal Salt Marsh Ecosystem of ...
Aug 16, 2024 · Furthermore, salt marshes serve to filter and purify adjacent estuaries and bays, sequester carbon from the oceans, and support economically ...
[64]
[PDF] Nutrients in Estuaries - U.S. Environmental Protection Agency
Eutrophication of Chesapeake Bay: His- torical trends and ecological interactions. Marine. Ecology Progress Series 303:1-29. With permission of the publisher ...
[65]
Regional reef fish assemblage maps provide baseline ... - Nature
Apr 3, 2024 · Spatial analyses of benthic habitats to define coral reef ecosystem regions and potential biogeographic boundaries along a latitudinal gradient.
[66]
Diversity on the edge:: non-linear patterns of coral community ...
Mar 21, 2018 · It is therefore likely that this narrow zone represents an ecotone ... complexity in coral reef ecosystems. Coral Reefs 32: 315−326. Graham ...
[67]
Spatial heterogeneity of coral reef benthic communities in Kenya
Aug 26, 2020 · In addition, the northern part of Kenya has been described as an 'ecotone' zone due to the presence of marginal/transitional coral reef ...
[68]
Spatial heterogeneity of coral reef benthic communities in Kenya
Aug 26, 2020 · This study described spatial patterns of coral reef benthic communities spanning across the 536-km coast of Kenya.
[69]
Coral Reef Carbonate Chemistry Reveals Interannual, Seasonal ...
Dec 26, 2023 · Ocean acidification (OA) threatens coral reef persistence by decreasing calcification and accelerating the dissolution of reef frameworks.
[70]
Effects of Ocean and Coastal Acidification on Ecosystems | US EPA
Apr 22, 2025 · Acidification can affect species differently, impacting food webs, and may dissolve coral skeletons, affecting entire ecosystems and human ...
[71]
Key study demonstrates buffering of some Florida reefs ... - Climate
Jan 29, 2024 · A more acidic ocean makes it harder for corals and other marine organisms to build their calcium carbonate skeletons and shells. However, ...
[72]
Tundra Vegetation to Grow Taller, Greener Through 2100, NASA ...
Aug 6, 2024 · The new NASA-led study finds an increased presence of trees and shrubs in those tundra regions and adjacent transitional forests.
[73]
New study shows Earth's coldest forests are shifting northward
Apr 19, 2022 · “Our study shows climate change is causing boreal trees and shrubs to expand into arctic and alpine tundra, while at the same time causing ...
[74]
Nutrients and Eutrophication | U.S. Geological Survey - USGS.gov
An overabundance of nutrients—primarily nitrogen and phosphorus—in water starts a process called eutrophication. Algae feed on the nutrients, growing, spreading ...
[75]
Increased invasion of submerged macrophytes makes native ...
Jan 20, 2024 · Invasion and eutrophication are considered to pose serious threats to freshwater biodiversity and ecosystem function.
[76]
Global impacts of future urban expansion on terrestrial vertebrate ...
Mar 25, 2022 · Global assessments show that urban expansion has caused about 50% loss of local within-site species richness (hereafter 'species richness') and ...Missing: ecotones 2020s
[77]
Environmental Impacts of Microplastics and Nanoplastics: A Current ...
The damaging effects of accumulated MNPs on the soil systems are unquantifiable; they interact with other potentially harmful elements and organic contaminants, ...
[78]
What Are Ecotones and How Do They Contribute to Biodiversity?
Oct 17, 2024 · Ecotones refer to transition areas where ecological communities, ecosystems and biotic regions coincide. These zones are rich in biodiversity, ...
[79]
https://doi.org/10.3391/mbi.2013.4.3.06
[80]
Biosphere Reserves - UNESCO
They are learning areas for sustainable development under diverse ecological, social and economic contexts, touching the lives of more than 250 million people.World Network of Biosphere · Asia and the Pacific · Europe & North America