What is a habitat assessment?
Habitats comprise physical and biological features important to species and assemblages. For this assessment, habitats are confined, primarily, to important physical factors. Biogenic features, such as reef-building organisms (often-termed as habitat-forming biota) will be included as appropriate. The physical and chemical environments of the Southern Ocean, combined, form the “physical habitat” that may affect organisms in a number of ways, depending on the suitability of the conditions:
(i) a medium/substratum in/on which to live,
(ii) the temperature of the surroundings,
(iii) availability of nutrients and other resources (food, light),
(iv) a vector for movement, and
(v) exposure to predation or other sources of mortality.
The aim here is to summarise the nature of habitats in the Southern Ocean and how they may vary in space and time.
An important outcome is to provide estimates of change in habitats for different Southern Ocean biota. Thus, habitat metrics reported here are those that will enable straight-forward policy-ready statements of change.
The habitat metrics will require consideration of spatio-temporal scales of primary importance to biota in the Southern Ocean and approximate the status and trends of habitats at those scales. Some metrics are comparatively unchanging, e.g. bathymetry, while others will need to be reported seasonally. In space, finer grain reporting occurs when taxa are restricted in their distributions, while coarser grain reporting, e.g. whole sectors, is suitable for widely distributed taxa.
Where possible, consideration will be given to changes that have occurred since the industrial revolution. As per the IPCC, we use 1750 as marking the beginning of the industrial period.
A habitat assessment has the following steps (here, the focus is on physical factors):
- Identify important physical parameters that can be summarised as an attribute of habitat of one or more species
- Identify the attributes to be derived from one or more parameters that are important to the species e.g. optimum temperature range important to the success of species
- Identify the quantity/quantities for expressing the status and trends of the attributes
- Establish links to the appropriate datasets and extract the quantities for presentation
Habitat classes identified for this assessment are:
- Light and atmosphere
- Integrated habitat measures