Student: Lidiia Iavorivska

For this assignment I am exploring a a partial attribute table from a feature class containing PA Farm Easements 2025, which is available from the Pennsylvania Spatial Data Access (PASDA) website. The dataset contains polygons of farmland preservation easement across Pennsylvania, which have been designated to preserve prime farmland through the Pennsylvania Agricultural Conservation Easement Purchase Program.

This analysis explores the size and number of agricultural land parcels purchased across the state over the years.

Load libraries

library(tidyverse)
library(here)
library(readr)
library(dplyr)
library(ggplot2)
library(ggpmisc)
library(knitr)

Read data and get column names

farms <- read_csv(here("tidyfarms.csv"))
names(farms) # print column names of the  file
##  [1] "fid"              "sitename"         "county"           "own_type"        
##  [5] "esmthldr"         "area_acres"       "shape_leng"       "est_year"        
##  [9] "pub_access"       "duration"         "landscape"        "new_acreage_comp"

Data preparation: Converting area (acres) to square feet

The “shape_length” field is in square feet, which shape area is in acres. Fr a meaningful ratio calculation, the area needs to be be converted to comparable units (square feet). The resulting column is added to a file and saved as a new “tidyfarms_updated.csv” file.

farms$area_sqft <- farms$area_acres * 43560

write_csv(farms, here("tidyfarms_updated.csv"))  # save the updated data set to a new file

farms <- read_csv(here("tidyfarms_updated.csv"))  # read in the new file for plotting
## Rows: 6615 Columns: 13
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## chr (7): sitename, county, own_type, esmthldr, pub_access, duration, landscape
## dbl (5): fid, area_acres, shape_leng, est_year, area_sqft
## lgl (1): new_acreage_comp
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

Relationship betwen parcel area and shape length

While examining agricultural easement parcels, I first looked at the relationship between the area (response variable) and length of each parcel (the only two continuous variables in this data set).

The parcels with a larger area relative to their length tend to be more compact, which is beneficial for farming because compact shapes are easier to cultivate, irrigate, and manage with machinery. In contrast, parcels that are long and narrow usually follow features like roads or streams and may reflect historical land divisions, but these shapes can make agricultural operations less efficient due to increased boundary relative to usable interior land. Analyzing this relationship can help understand how parcel shape can impact farming practicality and overall land management effectiveness.

Figure 1. Relationship between parcel shape length and area showing a smoothing line with standard error intervals (shaded). The plot illustrates how parcel area increases with length showing that longer parcels tend to be larger in total acreage and that parcel geometry. The smoother line reveals any nonlinear patterns in agricultural parcel geometry.

Figure 1. Relationship between parcel shape length and area showing a smoothing line with standard error intervals (shaded). The plot illustrates how parcel area increases with length showing that longer parcels tend to be larger in total acreage and that parcel geometry. The smoother line reveals any nonlinear patterns in agricultural parcel geometry.

Parcels by years of farm easement establishment

Parcel sizes

While the concept of conservation easements existed earlier, the statewide Pennsylvania Agricultural Conservation Easement Purchase Program was established in 1988 to help slow the loss of prime farmland to non-agricultural uses. The first easements were purchased to protect farmland in December 1989.

Figure 2. Distribution of parcel area (in acres) by year of establishment. The boxplot shows how parcel sizes vary across establishment years, with the median, interquartile range, and outliers highlighted. Note that parcels with a Zero year of establishemnt did not have specific years listed.

Figure 2. Distribution of parcel area (in acres) by year of establishment. The boxplot shows how parcel sizes vary across establishment years, with the median, interquartile range, and outliers highlighted. Note that parcels with a Zero year of establishemnt did not have specific years listed.

The data shows that the median parcel area has remained relatively stable across the years; however, the early years after the program’s establishment (from the early to late 1990s) had larger median parcels and significantly larger maximum parcel sizes, as indicated by the outliers. Overall, the median parcel size shows a downward trend over time, which makes intuitive sense given that agricultural land has been steadily declining nationwide as more land is converted to urban development.

Parcel number

Figure 3. Number of conservation easements established per year in Pennsylvania. The bar chart illustrates temporal trends in farmland conservation activity. Note that parcels with a Zero year of establishemnt did not have specific years listed.

Figure 3. Number of conservation easements established per year in Pennsylvania. The bar chart illustrates temporal trends in farmland conservation activity. Note that parcels with a Zero year of establishemnt did not have specific years listed.

When the number of parcels is plotted by year, it appears that while the largest easement parcels by area were mostly designated in the 1990s, the highest level of easement program activity occurred in the early and late 2000s, as shown by the higher number of parcels established during those years.