Ecological resilience in the context of "Nature-based solutions"

An ecosystem (or ecological system) is a system formed by organisms in interaction with their environment. The biotic and abiotic components are linked together through nutrient cycles and energy flows.

Ecosystems are controlled by external and internal factors. External factors—including climate—control the ecosystem's structure, but are not influenced by it. By contrast, internal factors control and are controlled by ecosystem processes; these include decomposition, the types of species present, root competition, shading, disturbance, and succession. While external factors generally determine which resource inputs an ecosystem has, their availability within the ecosystem is controlled by internal factors. Ecosystems are dynamic, subject to periodic disturbances and always in the process of recovering from past disturbances. The tendency of an ecosystem to remain close to its equilibrium state, is termed its resistance. Its capacity to absorb disturbance and reorganize, while undergoing change so as to retain essentially the same function, structure, identity, is termed its ecological resilience.

In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, the canopy is the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms (epiphytes, lianas, arboreal animals, etc.). The communities that inhabit the canopy layer are thought to be involved in maintaining forest diversity, resilience, and functioning. Shade trees normally have a dense canopy that blocks light from lower growing plants.

Early observations of canopies were made from the ground using binoculars or by examining fallen material. Researchers would sometimes erroneously rely on extrapolation by using more reachable samples taken from the understory. In some cases, they would use unconventional methods such as chairs suspended on vines or hot-air dirigibles, among others. Modern technology, including adapted mountaineering gear, has made canopy observation significantly easier and more accurate, allowed for longer and more collaborative work, and broaddened the scope of canopy study.

In ecology, an ecosystem is said to possess ecological stability (or equilibrium) if it is capable of returning to its equilibrium state after a perturbation (a capacity known as resilience) or does not experience unexpected large changes in its characteristics across time. Although the terms community stability and ecological stability are sometimes used interchangeably, community stability refers only to the characteristics of communities. It is possible for an ecosystem or a community to be stable in some of their properties and unstable in others. For example, a vegetation community in response to a drought might conserve biomass but lose biodiversity.

Stable ecological systems abound in nature, and the scientific literature has documented them to a great extent. Scientific studies mainly describe grassland plant communities and microbial communities. Nevertheless, it is important to mention that not every community or ecosystem in nature is stable (for example, wolves and moose on Isle Royale). Also, noise plays an important role on biological systems and, in some scenarios, it can fully determine their temporal dynamics.

Ecological threshold is the point at which a relatively small change or disturbance in external conditions causes a rapid change in an ecosystem. When an ecological threshold has been passed, the ecosystem may no longer be able to return to its state by means of its inherent resilience. Crossing an ecological threshold often leads to rapid change of ecosystem health. Ecological threshold represent a non-linearity of the responses in ecological or biological systems to pressures caused by human activities or natural processes.Critical load, regime shift, critical transition and tipping point are examples of other closely related terms.