Queries about project configuration in Eco

[gunjan_sharma]

Hi,

We conducted an i-Tree Eco survey on randomly sampled plots in parks across Christchurch city, New Zealand. I had the following questions about the project definition:

 1. Considering our focus on a single land use i.e., parks, I understand that when setting up the project and defining strata, we should use the area value of the single stratum (parks) rather than the area value of the entire city. However, I'm curious about the inclusion of urban population data during project definition. How is this population data utilized? Are the benefits normalized by population? Since our survey is specific to a single stratum, but the population represents the whole city, will this impact our results in any way?

2. In the model, our access to the most recent weather and pollution data for Christchurch is limited to the year 2019, with only weather data available for 2021. Given that our fieldwork was conducted during the summer of 2023-24, how can we get access to more recent weather and pollution data? Additionally, would it be more appropriate to select a recent year with precipitation values that deviate significantly from actual values, or opt for a less recent year with precipitation values closer to the average rainfall values?

Your insights would be greatly appreciated. Thank you.

[Jason.Henning]

The population data is used to estimate the relative number of people exposed to cleaner air due to trees. The population density is the value that is actually used in that calculation. Unless the population density is significantly lower near the parks you measured then there is no need to adjust the population or population density. For more details on how the population density is used to estimate the value of air quality benefits please see our Understanding i-Tree document and the relevant references. The air pollution removal section begins on page 24.
For areas outside the US the pollution and precipitation data are provided by in country partners. Those partners can choose to update the data regularly but there is a cost for the time is takes our scientists and software developers to validate and integrate that data. Individual users are welcome to provide more recent precipitation and pollution for their location through our i-Tree Database portal at no cost. Currently, we can only incorporate data through 2021. This is because we need a complete calendar year of data and the data must be merged with the underlying weather data we use. That weather data is from the NCEI. They only release full calendar years of data and typically it takes them about a year to release that data. It then takes us significant time to validate those global hourly data and incorporate the data sets into i-Tree Eco. For these reasons the data available in i-Tree Eco will always be two to three years behind the current year. In general it makes sense to select a year with typical rainfall amounts for your region unless you want to evaluate the effects of trees during particularly wet or dry years. Similarly, it is best to avoid years with wild fires or other events that may drastically increase air pollution beyond typical levels.
Thanks,
Jason