Mapping Britain’s hedgerows
Also: How the Iran war is hurting Donald Trump
Data journalist and interim special-projects editor
Could an unpopular war and rising fuel prices cost Donald Trump the midterms? Because petrol taxes tend to be lower under Republicans, an increase in the oil price leads to a steeper hike in prices at the pump in red states than in blue ones. History suggests that when fuel prices rise, voters are more likely to vote against the incumbent president. Gerald Ford, Jimmy Carter and George H.W. Bush all lost office after oil-price spikes. Mr Trump’s approval rating sits at -18. It is the lowest score for any president we’ve tracked at this point into their term. Follow our interactive tracker for more.
More of our data and visual reporting this week:
In 2021 2.3m people in China died because of air pollution, making up 19% of all deaths. And yet, after a period of rapid improvements, China’s fight against air pollution has slowed.
The world seems to be watching the Strait of Hormuz and at the same time eyeing petrol prices at the pump. Many are worried about fuel costs going up further if the blockade continues. But James Fransham crunched the numbers to find that in Britain driving a car has rarely been cheaper.
A new report shows that the Anglosphere is growing more miserable. But which country is the happiest in the world? And what can we learn from it?
Hedgerows have never struck me as an important feature of Britain’s landscape. But, as we reported in a recent article, they are vital for wildlife and play an important role in Britain’s ecosystem. Below Helen Atkinson explains how she visualised millions of hedges.
Mapping Britain’s hedgerows
Helen Atkinson
Visual data journalist
Britain has a lot of hedgerows. More than 16m hedges cover the countryside, bordering fields alongside walls, fences, trees and canopies. Our recent article explains why there are so many, and why the government is paying Britons to grow even more of them. But how do you map millions of hedges that cover over 200,000 square kilometres?
Ordnance Survey, Britain’s national mapping agency, meticulously collects, analyses and maintains the country’s geospatial data. One of its datasets records field boundaries, which are structures that separate fields from each other as well as from other types of land. The data are extremely detailed and interesting, but the file is rather large at 24GB—so my first task was to filter it for hedges and shrink the file size to have something more manageable to work with.
Top: All field boundaries, with hedges in green
Bottom: Filtered to just show hedges
We wanted to visualise the full extent of Britain’s hedgerows and the dataset allowed us to choose from length, area or volume. Although length is useful it doesn’t tell the full story. Volume didn’t seem like the right angle for a two-dimensional map. Instead I settled on showing the hedges as a share of land coverage, to get a broad sense of where they are most abundant and where they are sparse.
The data are formatted as lines, but include an average width attribute that I used to create approximate shapes for each hedge. To do this I used QGIS, an open-source mapping program. Its buffer tool allows me to create a shape around an existing feature. I added the widths to the lines and turned them into polygons (after some wrangling in R, a programming language, to calculate the buffer width—a much speedier alternative to calculating in QGIS). Then I trimmed off any overlaps so I wouldn’t overestimate the total hedge area later on.
Hedges turned into shapes
Once I had my hedge polygons, I created a grid (see below) to calculate the share of an area covered by the shrubbery. After trying a couple of different sizes (a single square km turned out too detailed; ten square km looked too sparse), I decided on the middle ground by going with a five-square-km grid. This had to be clipped to the outline of Britain to prevent misleading results around coastal areas, where part of the grid square might cover sea instead of land.
The grid clipped to the coastline
With the hedges and grid ready, I intersected the two layers—splitting any hedges that crossed grid boundaries so they wouldn’t be counted twice. Finally, I used the field calculator function in QGIS to put a figure on the area of each polygon. I added the results to my dataset as a new column.
The hedge polygons split between two grid cells, so that the shapes are contained within one cell
The final step was to actually calculate the area of each grid cell that was covered by the hedge polygons. This was done by joining the attributes of the grid with the hedge layer and employing the field calculator again to create a new column with the share of coverage.
The final map
The resulting map is testimony to the country’s love of hedges—in Cornwall there is a patch where nearly 7% of land is covered by the shrubbery. But there is still a long way to go until the government has restored the hedges that have been lost over time. About 72,500km, in fact.
How the Iran war is hurting Donald Trump
An unpopular conflict and costly fuel could hobble his presidency
Republicans should not panic, insists the White House. “NO PANICANS!”, it tweeted on March 14th. Nonetheless, signs of panic can be detected.