Disturbance

Biodiversity

Function

Summary

Disturbance ranges from small to large events and shapes biodiversity at multiple levels of organisations, with consequences for ecosystem functioning (Dornelas 2010). Ecological theory suggests that biodiversity will be maximised at intermediate levels of disturbance, which links to conservation management intervention e.g. grazing, predation (Dornelas 2010). However, higher intensity human-driven disturbance can have a negative impact on ecological communities (Dornelas 2010).

Disturbances cause temporary and localised shifts in demographic rates, influencing the numerical abundance of populations and relative abundance of species within communities (Dornelas 2010, Sousa 1984). Disturbance also affects ecosystem-level processes e.g. primary production, biomass accumulation, energetics, nutrient cycling (Sousa 1984).

Physical processes (e.g. fires, storms, floods, winds, landslides, drought) and biological processes (e.g. predation, grazing, digging) cause disturbance (Sousa 1984). These disturbance processes can be monitored at medium to large scales.

Methodology summary

Disturbance can be quantified as (Sousa 1984, Moloney and Levin 1996):

Area of disturbance
Magnitude of disturbance (intensity/severity)
Frequency of disturbance (random point frequency/regional frequency)
Predictability (variance in mean time between disturbances)
Turnover rate

Large-scale disturbance is captured in metrics of landscape-scale habitat dynamics: Patch persistence/turnover, Landscape diversity.

Medium-scale disturbance could be captured through assessment of metrics such as: herbivory, predation, patch dynamics (fine-scale disturbance), browsing/debarking, dung density.

Disturbance events are discrete in time and space and are usually temporary and localised. Changes in demographic rates as a consequence of disturbance can be captured by changes in abundance (Relative abundance, Mammal biomass, Invertebrate biomass, Vegetation biomass) and diversity (Species diversity) (see also Population fluctuations).

Disturbance effects on ecosystem processes can be captured by monitoring: Energy flow rates, Nutrient cycling rates, Vegetation biomass.

Metric threshold or direction of change

Thresholds not clearly defined, but disturbance is generally beneficial at an intermediate level. A desirable threshold and direction of change will be project specific.

Technological innovations

Earth Observation can measure intermediate-scale disturbance that is challenging to capture using field plots e.g. forest disturbance (Anderson et al. 2018, Masek et al. 2013, Wolter and White 2002).
Biological effects of inundation, fire disturbance, and pest and disease outbreaks can be captured by remote sensing (Skidmore et al. 2021).

Agricultural
Forest
Grassland
Heathland
Other
Peatland
Saltmarsh
Wetland

Scale

Landscape

Cost

Medium

Tier

Future

Technical expertise

Medium