D4.2 Stability and change

A stable ecosystem maintains its structure and functions despite disturbance or returns toward them after disturbance.

Resistance limits immediate change; resilience supports recovery; diversity, control loops and resource availability influence both.

Separate resistance from resilience before judging a disturbance response.; separate state, pressure, control loop and time

A diverse wetland may keep nutrient cycling during a heatwave and recover plant cover after water returns. This gives a concrete prediction from the stated ecosystem.

Stability is not permanent stasis; ecosystems can change while retaining key functions. Interpret the result within the stated model and evidence limits.

Ecosystem stability depends on suitable abiotic conditions, connected energy and nutrient flows, biodiversity, and control loops that prevent runaway change.

Removing one support can weaken others: habitat loss reduces diversity, which can reduce functional redundancy and recovery. Stability is therefore a system property.

Name the condition, the mechanism it supports, and the function that would fail if it changed.; separate state, pressure, control loop and time

If drought removes a key producer, less energy reaches consumers and the food web becomes less resilient to a second shock. This gives a concrete prediction from the stated ecosystem.

No checklist guarantees stability; interactions and timescales determine the outcome. Interpret the result within the stated model and evidence limits.

Removing rainforest changes habitat, carbon storage, water cycling and local climate, potentially reinforcing further forest loss.

Fewer trees reduce evapotranspiration and rainfall recycling; exposed soil dries and burns more easily; fragmentation weakens recovery and biodiversity.

Trace the pressure through at least two linked control loops before predicting a long-term shift.; separate state, pressure, control loop and time

A cleared patch becomes hotter and drier, making nearby seedlings less likely to establish and fire more likely to spread. This gives a concrete prediction from the stated ecosystem.

One case study cannot establish a universal threshold; outcomes depend on location, scale and management. Interpret the result within the stated model and evidence limits.

A mesocosm is a contained, simplified ecosystem used to test a disturbance while controlling some variables.

Replicated treatments allow comparison and measurement of change, but walls, small scale and missing species alter interactions. Mesocosms are models, not complete ecosystems.

Identify the manipulated variable, controls, measured response and limitation before generalizing.; separate state, pressure, control loop and time

Replicate ponds with different nutrient inputs can reveal algae and oxygen responses under the same light and temperature. This gives a concrete prediction from the stated ecosystem.

A mesocosm result supports a mechanism; it does not automatically predict a lake or ocean. Interpret the result within the stated model and evidence limits.

A keystone species has an effect on community structure much larger than its abundance would suggest.

Its predation, grazing, habitat engineering or other interaction controls competitors or resources. Removing it can trigger a trophic cascade and reduce diversity.

Predict the community change after removal by identifying the interaction the species controls.; separate state, pressure, control loop and time

Removing sea otters can allow sea urchins to increase and overgraze kelp forests, changing habitat for many species. This gives a concrete prediction from the stated ecosystem.

Keystone status is context-dependent; abundance alone does not identify a keystone species. Interpret the result within the stated model and evidence limits.

A harvest is sustainable when long-term removal does not exceed the population’s capacity to replace what is taken.

Growth rate, age structure, habitat, uncertainty and enforcement determine whether harvest leaves a viable breeding population. A short-term high catch can still cause long-term decline.

Compare removal with regeneration under the relevant stock and time conditions.; separate state, pressure, control loop and time

Catching fish below a precautionary quota while protecting spawning adults can keep recruitment above replacement. This gives a concrete prediction from the stated ecosystem.

A fixed quota is not automatically sustainable when climate or stock size changes. Interpret the result within the stated model and evidence limits.

Sustainable agriculture maintains production while conserving soil, water, biodiversity and future productive capacity.

Crop rotation, soil cover, efficient irrigation, nutrient matching and integrated pest control reduce erosion, depletion and pollution. Choice depends on climate, crop and farmer resources.

Evaluate a practice by its yield effect, resource cost, timescale and likely trade-offs.; separate state, pressure, control loop and time

A farmer rotates legumes with cereals and keeps soil covered, adding nitrogen while reducing erosion and fertilizer demand. This gives a concrete prediction from the stated ecosystem.

One practice can improve one resource while worsening another; assess the whole system. Interpret the result within the stated model and evidence limits.

Eutrophication is enrichment by nutrients that stimulates algal growth and can deplete oxygen when biomass decomposes.

Nitrate or phosphate runoff increases primary production; decomposition consumes dissolved oxygen; hypoxia stresses or kills aquatic organisms and changes the food web.

Trace nutrient input, algal response, decomposition and oxygen before naming the ecological effect.; separate state, pressure, control loop and time

Fertilizer runoff causes an algal bloom; after algae die, bacteria respire intensely and fish suffocate in the oxygen-poor water. This gives a concrete prediction from the stated ecosystem.

Not every algal bloom is nutrient-driven, and oxygen recovery depends on flow, depth and further inputs. Interpret the result within the stated model and evidence limits.

Biomagnification is the increase in concentration of a persistent, often fat-soluble pollutant at higher trophic levels.

The substance is not easily excreted; each predator consumes contaminated prey, so concentration rises through the food chain. Long-lived top predators receive the greatest exposure.

Check persistence, storage in tissue, trophic position and consumption before predicting risk.; separate state, pressure, control loop and time

A mercury concentration low in plankton becomes higher in fish and highest in fish-eating birds. This gives a concrete prediction from the stated ecosystem.

Biomagnification differs from bioaccumulation within one organism; not every pollutant magnifies. Interpret the result within the stated model and evidence limits.

Plastic pollution enters oceans through land and marine sources, persists as debris or fragments, and can harm organisms by ingestion, entanglement or chemical transport.

Breakage creates microplastics rather than eliminating material. Currents redistribute particles, while organisms can move them through food webs.

Identify source, transport pathway, exposure route and likely intervention point.; separate state, pressure, control loop and time

A lost fishing line entangles a turtle; a smaller fragment later enters plankton-feeding animals. This gives a concrete prediction from the stated ecosystem.

Plastic presence alone does not quantify ecological harm; polymer, size, dose and exposure matter. Interpret the result within the stated model and evidence limits.

Rewilding aims to restore self-sustaining ecological processes by reducing intensive control and, where appropriate, returning species or habitat structure.

Large herbivores, predators or natural disturbance can rebuild trophic interactions and heterogeneity. Outcomes depend on land use, conflict and monitoring.

Evaluate the process restored, the people affected and the evidence that management can be reduced.; separate state, pressure, control loop and time

Reintroducing beavers can create wetlands that slow water, increase habitat diversity and reduce downstream flood peaks. This gives a concrete prediction from the stated ecosystem.

Rewilding is not simply abandoning land; safety, invasive species and local livelihoods still require governance. Interpret the result within the stated model and evidence limits.

Ecological succession is the gradual change in species composition and community structure over time.

Early colonists modify light, soil, nutrients and microclimate, enabling or excluding later species. Disturbance and control loops determine the pathway.

Identify the starting condition, colonist effect and later community change.; separate state, pressure, control loop and time

After a field is abandoned, grasses alter soil and shade, allowing shrubs and eventually trees to establish. This gives a concrete prediction from the stated ecosystem.

Succession is not a fixed march to one climax everywhere; climate and disturbance alter pathways. Interpret the result within the stated model and evidence limits.

Primary succession starts on a surface lacking soil and usually proceeds through colonization, soil formation and increasing structural complexity.

Pioneer organisms weather substrate and add organic matter; later plants deepen soil and change resources. The process is slow because soil must develop.

Check whether soil and a biological legacy remain before calling a sequence primary.; separate state, pressure, control loop and time

Lichens colonize fresh volcanic rock, add organic matter, and help later mosses and vascular plants establish. This gives a concrete prediction from the stated ecosystem.

A cleared field with existing soil is secondary succession, even if most vegetation was removed. Interpret the result within the stated model and evidence limits.

Cyclical succession occurs when recurring disturbance repeatedly shifts a community through a predictable sequence without a single permanent endpoint.

Fire, flooding, grazing or seasonal conditions reset some species while survivors and propagules restart the pathway. Frequency and intensity set the cycle.

Compare disturbance interval with species life histories before predicting the recurring community.; separate state, pressure, control loop and time

A grassland burned every few years returns to fire-tolerant herbs rather than developing into forest. This gives a concrete prediction from the stated ecosystem.

A cycle is not random change; it requires a recurring driver and repeatable response. Interpret the result within the stated model and evidence limits.

A climax community is a relatively stable late-successional state under given conditions; arrested succession occurs when a pressure prevents progression.

Climate, soils and disturbance set the potential pathway. Grazing, mowing, fire or pollution can hold a community at an earlier stage.

Ask what disturbance or management maintains the observed stage and whether removing it would change the trajectory.; separate state, pressure, control loop and time

Continuous grazing can keep a grassland open and prevent shrub establishment, producing an arrested succession. This gives a concrete prediction from the stated ecosystem.

There is no universal permanent climax; stable states can shift when conditions change. Interpret the result within the stated model and evidence limits.