Over the years, gardeners have developed ways to keep the plants alive and beautiful. From prisoners with garden hoses to Shelagh Fritz and the water catchment system, the gardeners have worked with San Francisco’s climate to create beautiful flowers.
However, things are starting to change. Climate change is having an impact on the plants around Alcatraz. San Francisco used to have predictable and stable weather. It would rain from about November to January. It would be dry and foggy in the summer. And generally, the temperatures would stay between 50- and 70-degrees Fahrenheit year round, with a few days in August raising above. This predictable weather pattern is great for gardeners as it allows for planning. You can collect rainwater in the winter and then use what you collected throughout the summer to keep the gardens thriving. The lack of frost meant that plants could bloom longer and grow larger, something all gardeners want. While it’s true non-native plants can have a harder time with the climate, with proper care, they can thrive.
One of the first major signs of climate change affecting the plants on Alcatraz was the California drought. The drought from 2011 to 2017 was one of the worst in California’s history. 2011 to 2014 was the driest period in California history since record keeping began. In 2001, the annual precipitation was 25.03 inches. In 2011, the annual precipitation was 15.64 inches, nearly ten inches less than ten years previously (Data from Golden Gate Weather Services: https://www.ggweather.com/sf/monthly.html). Because of the drought, there wasn’t water available during the summer from the water catchment system. Even on areas where the island was not watered regularly suffered. The Persian carpet used to look very vibrant and pink on the cellhouse slope. Even after nearly three years of steady rainfall, it has yet to recover.
The average yearly temperature has also increased (see graph). The average temperature for the year has not been 55 degrees Fahrenheit since 1975. Two years in a row (1996 and 1997) the average temperature has been above 60 degrees Fahrenheit. And while an increase of about one or two degrees doesn’t seem like a lot, it can wreak havoc on the plants.
Frost is starting to appear on Alcatraz, which as any gardener knows, can cause plants to hibernate and in some cases die. Summers are experiencing less fog and winters less rain with the rain coming in short downpours that just runoff. Gardens and gardeners can adapt over time. However, what can be said for wild landscapes?