What are spatial layers?
In the context of the Spatial Portal of the Atlas of Living Australia, we use ‘layers’ to describe the concept of a surface draped over the landscape, where the spatial extent can be from a few tens of square kilometres to global scale. We have several hundred layers from ~70 data providers.
For a comprehensive report on the environmental and contextual layers in the Spatial Portal, see Towards a national bio-environmental data facility: experiences from the Atlas of Living Australia, Belbin and Williams (2015).
How to access spatial layers
You can see a summary of all available layers here, and from there, you can access more complete metadata for each layer.
When you download records of any species, group of species or lifeform, you can opt to append sampled values from any of the layers for each record. For example, you can append the value of mean annual temperature and the State/Territory of the records for all EPBC species.
You can use the Spatial Portal to view all available layers and use them in the various tools, for example in Species Distribution Modelling. To access a layer in the Spatial Portal, select from the menu option Add To Map | Layers.
How we classify spatial layers
Layers are classified using a three-level hierarchy. The first level has only two distinct types of layers: “environmental” and “contextual”.
Environmental layers are usually comprised of a regular spatial grid where the value for a grid cell can take a continuous value - for example, a layer of mean annual temperature in degrees centigrade of terrestrial Australia on a 1km grid. Generally, the environmental layers in the Spatial Portal are included because they are thought by experts to have some control or relationship with the distribution of organisms. For example, mean annual temperature is known to control the distribution of most species.
Contextual layers are usually comprised of polygons where each polygon takes a class value, for example the Australian States and Territories layers. Contextual layers provide an interpretation or implication of the distribution of species. These layers help with the management of species or areas. For example, we can determine which States and Territories are responsible for the management of a species or group of species, or how species are represented across Australia’s reserve network.
Classification levels two and three provide a concise summary of what type of information the layer contains. For example, the mean annual temperature layer mentioned above is classified as “Climate – Temperature” while the States and Territories layer is classified as simply “Political” with no finer (level 3) classification needed. In among the second level classification is the term “marine” to differentiate such layers from the more abundant terrestrial layers. Polygon classes are also added to the Spatial Portal’s gazetteer. For example, the IBRA 7 (bioregion) polygon called “Arnhem Coast” is added to the Spatial Portal’s gazetteer. This means that you can map these classes as ‘areas’ in the Spatial Portal’s Add to Map | Area function.
How we process spatial layers
Processing layers from many sources is not trivial, especially for the contextual layers. As occurrence records with a location are loaded into the ALA, every layer is sampled and the environmental values and contextual classes are appended to each record in our main database. We also correlate all environmental layers, so when selecting layers to display in the Spatial Portal, you will see a colour coding that provides an estimate of the level of correlation: Green means uncorrelated to the closest selected layer, orange is intermediate and red suggests high correlation. With contextual layers, this correlation takes the form of a cross-tabulation: All pairs of classes are examined for area (square kilometres), number of occurrence records and number of species, for example how many species are in national parks in NSW. Each layer added to our system adds significant processing overhead and impacts our index performance.
How we review and manage spatial layers
As can be appreciated, managing so many layers is far from easy. Are there updates available? Should older layers be deleted or maintained? What formats are the layers in? While such layers are not the primary responsibility of the ALA, we have taken on the task of collecting, processing and managing them because a) No one else was providing us with all the data we thought would be useful to users of the ALA, and b) we believe that there is great value to the ALA users in integrating of our species data with environmental and contextual data.
The current criteria for layer evaluation are:
- The information does not already exist (e.g., IPAs are in CAPAD)
- Is it an AREA (single or multi-polygon that could be imported/saved) rather than a layer?
- National coverage, or international coverage where data helps place the Australian region in context
- Presents information that suggests spatial control of species distributions or would be useful in the interpretation or management of species and areas
- Data is from an authoritative source
- Spatial resolution of 1km or better preferred
- Fills a gap in or complements our layer collection (name, space, time, environmental factor)
- Anticipated broad usage by one or more of the following communities (research, area managers, environmental consultants, citizen scientists, education, public)
- Has quality metadata
- Data is in a form that is readily ingested into our systems
- Is up to date
- Supersedes an existing layer (deprecation or deletion)
- Anticipates future requirements
- Supports nationally significant projects (which themselves would need some evaluation, but GBR management given World Heritage status and threats would pass)
- Openly available (free and open source data).
- Is externally funded.