Ecology — Textbook Reader

Ch 1Nature of Ecology

Ecology emerged as a distinct science in the late 19th century from Ernst Haeckel (coined "Oekologie" in 1866) and matured through 20th-century giants like Charles Elton (food chains, niche), G. E. Hutchinson (n-dimensional niche), and Robert MacArthur (community ecology). Modern ecology is increasingly quantitative — population dynamics use differential equations, community structure uses multivariate statistics, ecosystem fluxes use mass-balance models. The unifying question across all scales is "what determines the distribution and abundance of organisms?"

An ecologist studying a single species in isolation does autecology; one studying communities does synecology. The scientific method works in ecology, but with caveats: many systems are too large or slow for true experimental replication. Pseudoreplication — treating non-independent samples as independent — is a chronic statistical pitfall. Comparative observational studies, natural experiments (e.g., Mt. St. Helens, Yellowstone wolf reintroduction), and modeling complement true manipulative experiments.

A key conceptual tool is the distinction between adaptation, acclimation, and phenotypic plasticity. Adaptation is heritable trait change produced by natural selection across generations. Acclimation is reversible physiological adjustment within a single organism's lifetime (fur thickening in winter). Plasticity is the ability of one genotype to produce different phenotypes in different environments (cattail leaves growing taller in shaded conditions). All three create variation among individuals; only the first is evolutionary.

Ch 2Physical Environment — Climate

Earth receives ~342 W/m² average solar input ("insolation"). About 30% reflects (albedo) — snow ~0.8, forests ~0.1, ocean ~0.1. The 70% absorbed re-radiates as longwave IR. Greenhouse gases (water vapor, CO₂, CH₄, N₂O, O₃, CFCs) absorb that IR and warm the lower atmosphere; without them, Earth would be ~33 °C colder. Anthropogenic CO₂ (now ~425 ppm vs ~280 pre-industrial) is the dominant additional warming forcing of the past 150 years.

Earth's 23.5° axial tilt creates seasons. Equatorial regions get nearly direct insolation year-round; high latitudes have huge seasonal swings. The atmosphere responds via three convective cells per hemisphere. The Hadley cell dominates the tropics: warm air rises at the equator (rainforest), travels poleward at altitude, descends near 30° latitude (deserts — Sahara, Sonoran, Australian Outback). The Ferrel and polar cells create the temperate westerlies and polar easterlies.

The Coriolis effect deflects moving air masses — right in the Northern Hemisphere, left in the Southern — creating prevailing winds (trade winds easterly in tropics, westerlies in temperate). On longer timescales, the El Niño-Southern Oscillation (ENSO) shifts global precipitation patterns: warm-phase El Niño weakens trade winds, drowns equatorial Pacific in warm water, drives drought in Australia/Indonesia and flooding in Peru. The North Atlantic Oscillation shifts wet/dry between northern and southern Europe.

Microclimate matters more to small organisms than to large ones. A south-facing rocky outcrop, an oak's understory, a beaver's lodge interior — each has temperature, humidity, and wind regimes that differ markedly from regional climate. Many species' realized ranges are constrained by microclimate availability rather than regional climate per se.

Ch 3Aquatic Environments

Water's hydrogen bonding gives it remarkable properties: high specific heat (slow temperature change buffers aquatic life from rapid weather extremes), high heat of vaporization, and the unusual property of being densest at 4 °C. Ice floats — protecting deep aquatic life beneath winter ice. As polar solvent, water dissolves salts, sugars, and nutrients, but excludes hydrophobic compounds (a critical evolutionary force on membrane structure).

Lakes stratify thermally in summer. The epilimnion (warm, well-mixed surface) sits atop the thermocline (steep temperature gradient), which sits atop the hypolimnion (cold, dense, often hypoxic bottom). The thermocline is a density barrier blocking mixing; nutrients accumulate below, oxygen accumulates above. Spring and fall turnover occurs when surface water cools (or warms) to the same density as deep water, breaking stratification — wind mixes the lake top to bottom, redistributing oxygen and nutrients.

Lakes are classified by trophic state. Oligotrophic lakes are nutrient-poor, deep, clear, and cold (Crater Lake, Lake Tahoe). Eutrophic lakes are nutrient-rich, shallow, warm, and prone to algal blooms (most lowland lakes after centuries of agriculture). Movement between states can be reversed but is slow and expensive (Lake Erie's restoration took decades).

Marine systems differ. The ocean is alkaline (pH ~8.1) and well-buffered by the carbonate system: CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺ ⇌ CO₃²⁻ + 2 H⁺. This buffer is being challenged by anthropogenic CO₂ — ocean acidification has dropped surface pH by ~0.1 units since 1750 (a 26% increase in [H⁺]). The decrease in carbonate ion concentration impairs shell formation by corals, mollusks, and calcifying plankton.

Estuaries — where rivers meet the sea — show a salinity gradient from freshwater (<0.5 ppt salts) through brackish (0.5–30 ppt) to marine (30–37 ppt). Estuaries are extraordinarily productive due to nutrient loading from rivers; they nursery many marine fish. Salt-wedge estuaries (Mississippi delta) have a stratified denser saltwater layer pushing under freshwater outflow.

Ch 4Terrestrial Environments — Soil

Soil forms over thousands of years from five interacting factors (Hans Jenny's CLORPT: Climate, Organisms, Relief/topography, Parent material, Time). Vertical horizons develop: O (organic litter on top) → A (topsoil — dark, humic, biologically active) → E (eluviated/leached zone) → B (subsoil — accumulation of clay + Fe/Al oxides) → C (parent material) → R (bedrock).

Soil texture is the % of sand (large particles, drains fast), silt (medium), and clay (microscopic, holds water + nutrients). Loam is the goldilocks balance. Clay particles are negatively charged and hold cations like Ca²⁺, K⁺, Mg²⁺, NH₄⁺ via electrostatic attraction — the cation exchange capacity (CEC). Plants take up these cations by exchanging H⁺ from their roots, slightly acidifying soil over time.

Field capacity is the soil moisture remaining after gravity drainage. Wilting point is moisture below which plants can't extract water. Difference = plant-available water. Soil pH governs nutrient availability: at low pH (acid), Al³⁺ + Mn²⁺ become toxic and P binds to Fe/Al; at high pH (alkaline), Fe + Mn + P become unavailable. Most plants do best at pH 6–7.

Ch 5Plant Adaptations

C3 photosynthesis uses RuBisCO directly to fix CO₂. Most plants use C3. RuBisCO has a quirk: at high T it also accepts O₂, producing useless 2-phosphoglycolate (photorespiration), wasting energy. C3 dominates cool/wet climates where photorespiration is minimal.

C4 photosynthesis evolved repeatedly in tropical grasses + warm-climate plants. PEP carboxylase in mesophyll cells fixes CO₂ as oxaloacetate, which gets pumped to bundle-sheath cells where RuBisCO operates in a high-CO₂, low-O₂ environment. Net effect: CO₂ concentrating mechanism that suppresses photorespiration. C4 plants outperform C3 in hot/sunny conditions: corn, sugarcane, sorghum, most tropical grasses.

CAM (Crassulacean Acid Metabolism) — found in cacti, agave, pineapple — opens stomata at night to fix CO₂ as malate (stored in vacuoles). During the day, stomata close (water-saving) and stored malate releases CO₂ for RuBisCO. CAM is the supreme water-saving strategy at the cost of low growth rate.

Ch 6Animal Adaptations — Thermal Strategies

Ectotherms (reptiles, fish, most invertebrates) have body T ≈ environment. Costs little metabolically; thermoregulate behaviorally (sun-basking, microhabitat choice). At low T, metabolism slows — ectotherms are cold-limited but cheap to run. Endotherms (mammals, birds) maintain body T metabolically. Always-on heat production demands ~10× more food than equivalent ectotherm. Heterotherms switch modes: hummingbirds nightly torpor, ground squirrel hibernation, bats daily torpor.

Bergmann's rule: endotherms in colder climates tend to be larger (lower SA:V → less heat loss). Allen's rule: appendages shorter in cold (less SA per volume). Countercurrent heat exchange: arteries + veins running antiparallel transfer heat back to the body before reaching cold extremities — penguin feet, polar bear toes.

Other key animal adaptations: migration (seasonal movement to better conditions; high energy cost during transit but escape harsh season), hibernation (low metabolic activity in fat-stored state through winter), diapause (insect dormancy programmed by photoperiod). Q10 measures temperature sensitivity of biological rates (most enzymatic processes Q10 ≈ 2–3, meaning rate doubles per 10°C increase).

Ch 7Population Properties

Population density is individuals per unit area. Dispersion patterns: clumped (most common — patchy resources, social groups), uniform (territoriality producing even spacing), random (rare; requires no interactions). The pattern is scale-dependent — pine trees might be clumped at landscape scale (riparian) but uniform at fine scale (allelopathic spacing).

Survivorship curves: Type I (high juvenile survival, mortality concentrated late — humans, elephants), Type II (constant mortality across all ages — birds, small mammals), Type III (high juvenile mortality, survivors live long — fish, oysters, plants). Plotted as log(survivors) vs age.

A life table tracks survival + reproduction by age. Two flavors: cohort (follows a real birth cohort through life — best for plants, hard for long-lived animals) and static (snapshot of all current ages, assumes stable population). Net reproductive rate R₀ = Σ l_xm_x = average lifetime offspring per female. R₀ = 1 means stable; R₀ > 1 grows; R₀ < 1 declines.

Ch 8Population Growth Models

Carrying capacity K is the equilibrium where birth + death rates balance — set by limiting resources (food, water, nesting sites). K isn't fixed: drought lowers K for grazers, eutrophication raises K for cyanobacteria.

The r-K continuum distinguishes life-history strategies: r-selected species (small body, short lifespan, many small offspring once or early, density-independent regulation, disturbed/unpredictable habitats — insects, dandelions, weedy plants) vs K-selected species (large body, long-lived, few large offspring repeated, density-dependent regulation, stable habitats — whales, oaks, K. elephants). It's a continuum, not a strict dichotomy; many species span the middle.

Ch 9Life History Evolution

Semelparity: one reproductive event, then die (Pacific salmon, agave, mayflies). Favored when adult survival is unreliable — pour everything into one big effort. Iteroparity: repeat reproduction over a lifetime (most mammals + birds). Favored when adult survival is reliable + future reproductive opportunities exist.

The classic trade-off curve: many small offspring vs few large offspring. Bigger offspring survive better, but each costs the parent more. Optimum depends on environment + sibling competition + maternal condition. Coral spawning releases millions of eggs (Type III, semelparous); elephants invest 22 months gestation in one calf (Type I, iteroparous).

Reproductive value at age x = expected future reproductive output. Generally peaks just after age of first reproduction and declines. Senescence — decline of physiological function with age — is a consequence of selection acting weakly on traits expressed late in life (when most individuals would have died from external causes anyway).

Ch 10Population Regulation

Density-dependent factors intensify with population size and stabilize populations: competition, disease transmission, predator success. Density-independent factors act regardless of population size: weather, fires, floods. Real populations integrate both. The Allee effect describes per-capita rates DECREASING at very low densities (mate finding fails, group-defense fails, cooperative hunting fails). Below threshold, populations spiral toward extinction even without environmental harm.

Metapopulations are sets of local populations connected by dispersal. Source habitats have births > deaths (export individuals); sinks have deaths > births (require immigration to persist). Fragmentation often converts continuous populations into source-sink networks. If sources are lost, sinks crash.

Ch 11Competition

Intraspecific competition (same species) is strongest because resource needs overlap completely. Interspecific competition (different species) drives community structure. Two modes: exploitation (indirect — one consumer reduces resource for another) and interference (direct — territoriality, allelopathy, aggression).

Gause's competitive exclusion principle: two species with identical niches cannot coexist; one wins. Coexistence requires niche differentiation — resource partitioning (MacArthur's spruce-canopy warblers feeding in different vertical bands), character displacement (traits diverge in sympatry to reduce overlap), or temporal/spatial separation.

Tilman's R\* rule (resource competition): the species that drives the limiting resource to the lowest equilibrium concentration wins. R\* is measurable directly; simpler than Lotka-Volterra. Apparent competition: two prey species share a predator, who builds up on one prey + reduces the other — looks like competition without resource overlap.

Ch 12Predation, Herbivory, Parasitism

Three predator-prey functional responses (Holling 1959): Type I linear (filter feeders); Type II hyperbolic, saturating due to handling time (most predators); Type III sigmoidal (prey switching, search images, generalist predators). The numerical response is the predator population's growth in response to prey density.

Optimal foraging theory: predators evolve to maximize energy gained per unit time, balancing search + handling. Cumulative effect: predators tend to specialize on most-profitable prey when abundant + diversify when scarce. Lotka-Volterra predator-prey equations produce 90°-out-of-phase oscillations — empirically supported by lynx-snowshoe hare 10-year cycle.

Defenses include aposematism (warning coloration in toxic prey — monarch), Batesian mimicry (palatable mimics toxic — viceroy), Müllerian mimicry (multiple toxic species converge on shared signal — Heliconius butterflies). Plants deploy chemical defenses (tannins, alkaloids, glucosinolates) that may be constitutive or induced by herbivory.

Parasitism (+/− benefit/harm) doesn't kill immediately; parasitoids (parasitic wasps) lay eggs in/on hosts, larvae eat host alive. Both shape host populations + drive coevolutionary arms races.

Ch 13Parasitism + Disease Ecology

Parasites are typically smaller than hosts, often live within them, exhibit strong host specificity, and can be transmitted directly or via vectors. Macroparasites (helminths, ectoparasites) cause harm proportional to load; microparasites (bacteria, viruses, protozoa) reproduce rapidly within hosts and transmit horizontally.

R₀ in epidemiology = basic reproductive number = expected secondary cases per primary case in a fully susceptible population. R₀ > 1 → epidemic; R₀ < 1 → fade-out. Vaccines work by reducing the susceptible pool below R₀ threshold (herd immunity).

Population-level effects: parasites can regulate host density, drive host coevolution (Red Queen dynamics — must keep evolving to avoid being parasitized), and alter community structure via apparent competition between hosts sharing parasites.

Ch 14Mutualism + Commensalism

Mutualism (+/+) is widespread + ecologically important. Major examples: mycorrhizae (~80% of plants — arbuscular fungi penetrate root cortex cells; ectomycorrhizae sheath roots without entry, mostly in trees), nitrogen-fixing root nodules (Rhizobium ↔ legumes), coral-zooxanthellae (Symbiodinium dinoflagellates inside coral cells provide ~90% of coral energy), pollination syndromes (flower morphology matched to pollinator), gut symbionts (rumen bacteria + termite protozoa digesting cellulose).

Mutualism stability requires mechanisms preventing cheaters (individuals taking benefit without giving). Examples: legumes "sanction" non-fixing rhizobia by withholding O₂; cleaner fish that bite client get attacked by other clients. Commensalism (+/0) is rare; most apparent commensals turn out to be subtly costly to the "neutral" partner.

Coevolution: reciprocal evolutionary change between interacting species (predator-prey, host-parasite, plant-pollinator). Often diffuse — species coevolve with whole guilds rather than 1:1 partners.

Ch 15Community Structure + Diversity

Species richness (S) is the count of species. Evenness measures how equally abundance is distributed. The Shannon-Wiener index H' = −Σ pᵢ ln(pᵢ) integrates both. Simpson's index = probability that two randomly drawn individuals belong to different species.

Whittaker's hierarchy: α = within-site, β = turnover between sites, γ = total regional diversity. Approximation γ ≈ α × β. High β indicates each site has different species (heterogeneous landscape); low β indicates similar communities throughout.

Keystone species have disproportionate effect relative to abundance — Paine's classic Pisaster sea star removal experiment showed mussel monoculture and >15 species lost. Foundation species are similar but high abundance — they define physical structure (kelp, oak, coral). Ecosystem engineers physically modify habitat (beavers, prairie dogs, corals).

Top-down vs bottom-up control: Bottom-up = nutrients limit primary producers, which limit consumers up the chain. Top-down = predators control prey, with cascading effects to producers (trophic cascade — Yellowstone wolves → elk → willow). Most communities show both, with relative strength varying by system.

Ch 16Succession

Primary succession proceeds on bare substrate with no soil (volcanic flow, glacial retreat, sand dunes). Lichens + mosses pioneer; weather rock + accumulate humus over decades-centuries. Secondary succession happens with soil + propagule banks intact (after fire, agriculture, logging) — much faster, decades to a century.

Three classical mechanisms (Connell-Slatyer 1977): facilitation (early species improve conditions for later — alder fixing N enables spruce), inhibition (early species prevent later from establishing), tolerance (later establish despite earlier — depend on tolerating low light/nutrients). Real successions blend all three.

The Intermediate Disturbance Hypothesis (Connell 1978): diversity peaks at moderate disturbance frequency/intensity. Too little disturbance → competitive exclusion → diversity drops. Too much → only stress-tolerant ruderals survive. Mid is the sweet spot. Historical climax-community concept (Clements 1916) gave way to non-equilibrium dynamics.

Ch 17Fire Ecology — Bragg's Specialty

A fire regime is the characteristic frequency, intensity, season, type, and patchiness of fire in an ecosystem. Surface fires burn understory + litter (typical of grasslands + savannas — Bragg's prairies). Crown fires burn canopy (catastrophic, common in conifer forests). Fire intensity (heat output) differs from severity (ecological impact); severity depends on intensity AND ecosystem properties.

Pyrogenic adaptations in plants:

• Serotinous cones (jack pine, lodgepole pine) — resin-sealed, open only after fire heat → seeds drop on bare ash-fertilized seedbed.
• Thick bark (oak, ponderosa pine) — insulates cambium from surface fire.
• Basal sprouting (eucalyptus, oak) — regenerate from belowground meristems after top-kill.
• Smoke-cued germination (chaparral, fynbos species) — karrikins in smoke trigger seed germination.
• Pyriscence — synonym of serotiny in some texts.

Tallgrass prairie historically burned every 3–5 years. Fire suppresses woody invasion, recycles nutrients (rapid mineralization), and stimulates C4 grass productivity (warm-season grasses with belowground perennating organs survive while cool-season + woody plants get killed). Without fire, eastern red cedar + sumac + invasive forest species establish, shade out the C4 grasses, and tallgrass prairie converts to woodland within decades. Bragg has documented this woody encroachment process across decades of monitoring.

Bragg's published work spans:

• Effect of fire season (spring vs summer vs fall vs winter burns) on prairie plant community composition + seedbank germination.
• Effect of fire frequency (annual vs 3-yr vs 5-yr burns) on woody encroachment + forb diversity.
• Restoration ecology of Loess Hills prairie (wind-deposited silt cliffs along Missouri River, western Iowa / eastern Nebraska).
• Australian outback fire studies — fire effects on plant community of Western Australian desert grasslands.

Ch 18Ecosystem Energy Flow

Gross primary productivity (GPP) is total photosynthesis per unit area + time. Net primary productivity (NPP) = GPP − plant respiration. NPP is the energy available to consumers. Globally NPP is ~105 Pg C/yr terrestrial + ~50 Pg C/yr marine.

The 10% rule (Lindeman 1942): only ~10% of energy at one trophic level reaches the next. Most energy is lost as heat (2nd law) and as biomass not consumed. This limits food chain length to ~4–5 trophic levels.

Eltonian pyramid: pyramid of energy is always pyramid-shaped. Pyramid of biomass is usually pyramidal but can invert in open ocean (small fast-turnover phytoplankton supports larger zooplankton biomass at one moment). Pyramid of numbers is variable.

Detritus food chains often process more energy than grazing chains — terrestrial systems may move >50% of NPP through dead organic matter + decomposers. Decomposers (bacteria, fungi) + detritivores (earthworms, isopods, collembola) recycle nutrients.

Ch 19Biogeochemical Cycles

Phosphorus cycle has NO atmospheric pool (no significant P gas). Rock weathering releases phosphate → soil → biota → decomposers return to soil. Often the limiting nutrient in fresh waters + forests on old soils. Mining of P fertilizer is creating long-term sustainability concerns.

Carbon cycle: photosynthesis ↔ respiration is the largest flux. Combustion of fossil fuels adds ~10 Gt C/yr. Half absorbed by ocean + land sinks; rest accumulates in atmosphere.

Liebig's Law of the Minimum: productivity is constrained by the single most-limiting nutrient. Adding non-limiting nutrients won't help. Eutrophication: anthropogenic N + P → algal bloom → decomposition → hypoxic dead zones (Gulf of Mexico, Chesapeake Bay).

Ch 20Biomes

Biomes are major climate-defined vegetation types. The Whittaker biome diagram plots biomes on temperature × precipitation axes — useful for predicting biome shifts under climate change.

• Tropical rainforest — warm + wet year-round, highest biodiversity, low-fertility soils (nutrients in biomass), 200+ tree species/ha.
• Tropical savanna — warm with seasonal rain, grass + scattered trees, fire-maintained.
• Desert — <25 cm/yr precipitation, hot or cold, CAM plants + ectotherms dominate.
• Temperate grassland — Nebraska's biome; hot summer, cold winter, moderate rain. Tallgrass prairie (east) → mixed → shortgrass steppe (west). Fire-maintained.
• Mediterranean / chaparral — hot dry summer + mild wet winter. California, Mediterranean basin, Cape Town. Fire-maintained.
• Temperate deciduous forest — Eastern US; 4 seasons, 75–150 cm rain; oak, hickory, maple.
• Boreal forest / taiga — long cold winter; conifers (spruce, fir, pine).
• Tundra — permafrost, short growing season; mosses, lichens, dwarf shrubs.

Mountains compress latitudinal biome zones into elevational zones — climbing 1000m mimics traveling ~1000 km poleward (lapse rate ~6.5°C/km).

Ch 21Biogeography + Island Biogeography

MacArthur + Wilson's theory of island biogeography (1967): species number on an island = balance of immigration (declining with distance to mainland) and extinction (declining with island area). Larger + closer islands have more species at equilibrium.

Species-area relationship: S = cA^z, where z typically 0.15–0.4. Doubling area increases species ~10–25%. Used in conservation to predict species loss from habitat reduction.

Habitat fragmentation creates more edges + smaller cores + isolated patches. Edge effects (wind, light, predator penetration) hurt interior specialists. SLOSS debate — Single Large Or Several Small reserves? — depends on whether you prioritize total interior area or species turnover.

Ch 22Biodiversity

Biodiversity has multiple meanings: genetic (within-species variation), species (richness + composition), ecosystem (variety of habitats). Hotspots (Myers et al.) combine high endemism + high threat (~36 globally — Madagascar, Cape Floristic Province, Atlantic Forest).

The latitudinal diversity gradient — more species in tropics — is one of the strongest patterns in ecology. Many proposed explanations: greater area, more energy, more time, milder selective regime, faster diversification. Probably no single answer.

Human impact: ~1 million species threatened with extinction (IPBES 2019). Background extinction rate ~0.1–1 species/million species/year; current rate is ~100–1000× higher → "Sixth Mass Extinction." Drivers (acronym HIPPO): Habitat loss, Invasive species, Pollution, Population (human), Overharvest. Climate change increasingly competes for top spot.

Ch 23Conservation Biology

Conservation biology is a "crisis discipline" applying ecological principles to slowing extinction + restoring degraded systems. Key concepts: Minimum viable population (MVP) — smallest population with ~95% probability of persistence over a defined interval (often 100 yr). 50/500 rule (Franklin 1980) — Ne > 50 to avoid short-term inbreeding, Ne > 500 for long-term evolutionary potential.

Restoration ecology: actively reassembling degraded ecosystems. Bragg's prairie burning experiments are restoration ecology — testing how to manage tallgrass prairie remnants for community composition + diversity. Rewilding: restoring keystone species + reducing human management (Yellowstone wolves, European bison).

Genetic rescue: introducing individuals from other populations to small inbred ones — Florida panthers boosted by Texas pumas in 1995 → fitness recovery. Assisted migration: aided dispersal beyond current range to track climate change. Controversial — ecological + ethical concerns.

Ch 24Climate Change + Ecology

Atmospheric CO₂ has risen from ~280 ppm (pre-industrial) to ~425 ppm (2024). Global mean temperature has risen ~1.2°C since pre-industrial. Ecological effects: phenology mismatches (caterpillars hatching before bird migration; corals + zoox de-syncing), range shifts (~6 km/decade poleward, ~10 m/decade upslope), ocean acidification, coral bleaching mass events (1998, 2002, 2010, 2016, 2017, 2024 documented), species extinctions (Bramble Cay melomys 2016 — first mammal extinction directly attributed to climate change).

Feedback loops amplify or dampen change. Albedo feedback: ice melts → darker ocean exposed → more absorption → more melt. Permafrost-carbon feedback: warming releases stored C as CO₂ + CH₄ → more warming. Cloud feedback uncertain.

Mitigation requires reducing emissions; adaptation requires adjusting ecosystem management. Ecologists contribute by quantifying carbon stocks (forest, peatland, ocean), projecting ecosystem services under future climate, and designing adaptation strategies.