How is the tree cover trend versus surrounding area calculated?

Trends in tree cover are calculated using data on woody cover from the National Forest and Sparse Woody dataset. The data are an annual time series in which 25 m grid cells are classified as either non-woody, sparse woody (sub-forest woody cover where crown cover is between 5-19%) or forest (woody vegetation ≥2 m tall with crown cover >20%). The phrase “tree cover” is used here to refer to areas with sparse woody or forest cover.

The trends forest and sparse woody cover in the project’s carbon estimation areas (CEAs) (or project area where CEA data have not been released) for each year from the year the project was registered are compared to the trends in forest and sparse woody cover in the area surrounding the project.

The surrounding area, or buffer, to which each project’s tree cover trend is compared is, by default, the area 3 km wide outside the project boundary, excluding other HIR project areas. The boundary of the buffer area is shown on the map as a broken white line. Users can alter the buffer distance using the control at the top right of the map window.

The Explorer calculates the percentages of forest, sparse woody and non-woody pixels in the project’s CEAs (or project area) and the buffer, for each year from the year the project was registered. Simple linear models are fit separately to the time-series of the forest and sparse woody percentages, in the project’s CEAs (or project area) and buffer, with the percentage of each cover class as the response variable and year as the only independent variable. The differences between the slopes of those relationships are used to compare woody cover trends for the project and buffer, provided there are at least three data points in the time series. Projects without three data points receive a “Not enough data” badge.

Positive trends

Projects are given a “Positive” trend badge if they satisfy either of the following conditions.

Positive badge condition 1:

  • the percentage of woody pixels (forest or sparse woody) in the project’s CEAs (or project area) has not declined since the project was registered (sum of slopes for forest and sparse classes ≥ 0); and
  • the percentage of pixels with forest cover in the project’s CEAs (or project area) has not declined since the project was registered (forest slope ≥ 0); and
  • the difference between the slopes of the linear models for forest cover in the     project’s CEAs (or project area) and buffer is greater than 0.25% per year.

Positive badge condition 2:

  • the percentage of pixels with forest cover in the project’s CEAs (or project area) has not declined since the project was registered (forest slope ≥ 0); and
  • the percentage of pixels with sparse woody cover in the project’s CEAs (or project area) has not declined since the project was registered (sparse slope ≥ 0); and
  • the difference between the slopes of the linear model for forest cover in the project’s CEAs (or project area) and buffer is greater than -0.05% per year; and
  • the difference between the slopes of the linear model for sparse woody cover in the project’s CEAs (or project area) and buffer is greater than 0.25% per year.

Neutral trends

Projects that fail both of the conditions for a positive badge are given a “Neutral”trend badge if they satisfy the following condition:

  • the percentage of pixels with forest cover in the project’s CEAs (or project area) has not declined since the project was registered (forest slope ≥ 0); and
  • the difference between the slopes of the linear model for forest cover in the project’s CEAs (or project area) and buffer is greater than -0.05% per year; and
  • the difference between the slopes of the linear model for sparse woody cover in the project’s CEAs (or project area) and buffer is greater than -0.05% per year.

Projects that do not satisfy either the “Positive” or “Neutral” badge conditions receive a “Worse” trend badge.

The Timeseries tab provides graphs of the data for the three cover classes over time, for the project (CEAs or project area) and buffer, including the period from 1988 to project registration. Users can select buttons for non-woody, sparse or forest to change the cover class shown on the comparison graph. The “Download data” button provides a comma-delimited text file containing proportions for the three cover classes through the time series for the project and its buffer.

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Carbon Integrity Explorer

The Carbon Integrity Explorer provides information about carbon offsets projects registered under the Australian Government’s carbon offset scheme. 

Registered projects can generate Australian carbon credit units (ACCUs). Each ACCU is supposed to represent 1 tonne of real and additional abatement of greenhouse gas emissions. 

The Carbon Integrity Explorer uses government datasets to provide indicative information on whether projects are likely to be generating real and additional abatement.   

The information contained in the Explorer is indicative only and should not be relied upon as a definitive measure of the extent to which projects have, or are likely to, generate real and additional abatement. The Explorer does not:·  

  • assess, or purport to provide information on, whether projects are complying with the legal requirements of the offset scheme;  
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The Centre for Environment and Integrity Pty Ltd does not suggest or imply that any proponent of any project has done anything unlawful or unethical or that ACCUs issued to any project are not legitimate or valid. The indicative risk rating is an indicative measure of the abatement risk associated with relevant projects and nothing else. 

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