During this project, community scientists and partners of the Earthwatch Urban Resiliency Program collected leaf samples from 122 different tree species in the 43 parks surveyed. This includes many iconic native species such as the native oaks (coast live oak, Engelmann oak, and valley oak), as well as many exotics. California sycamores, Chinese elms, coast live oaks, and jacarandas were found in close to 50% of the parks surveyed, but many species were found only in a small number of parks.
- More than 700 people participated
- Over 14 partners engaged
- Program covered wide area ranging from Santa Monica to Reseda Park to Riverside
- Success collecting a wide diversity of species – 122 species
- 43 parks visited and mapped
All of the data collected has made it possible for us to look at three questions:
- How many different kinds of trees are we finding in the parks surveyed?
- How green are our parks?
- What are the leaves from the trees we sampled telling us about how they are faring?
The project identified and helped collect data on a large number of different species. This diversity of trees is important as wildlife habitat but also provides the project an amazing opportunity to better understand the diversity of trees in southern California.
Some parks in the study have many species, but 25% have a limited number of species (5 or fewer), which is similar to citywide tree species diversity.
Of the 43 parks that we assessed, we found an average of 10 species per park. Some parks has a very high number of tree species, including Eldorado (31 species), Hollydale (29 species), the Natural History Museum (25 species), Cheviot Hills (24 species). This average is similar to what project scientist Darrel Jenerette and his colleagues found when they sampled random plots across Los Angeles, Orange, and Riverside counties. While several parks have a great diversity of species, 25% only have 5 or fewer species.
An initial set of the raw data is available here: Earthwatch Park Data_NASA
By looking at the difference between a park’s green score and its surrounding city, we can see parks which are providing the most green benefits.
The nature (i.e. greenness) of parks can provide us with many benefits such as cooling, stress relief and wildlife habitat. Also, vegetation needs water to prosper, which may be challenging during times of water limitation.
We were able to figure out degree of greenness of the parks by using the imagery taken by the NASA Hyspi flyover during the project. Using sophisticated software, we can use the outlines of each park to measure how much green “color” there is inside the boundaries of each park. Scientists call this measure of greenness “Normalized Difference Vegetation Index”, or NDVI.
We were also able to assess the degree of greenness in the neighboring cities where each park was found giving us a sense of how much each park is a true island of green surrounded by gray – and just how important it might be for the people who live there. For reference sake, values close to zero would be barren rock, values between 0.2 and 0.4 being mostly grass and shrubs, and full forests would be a one.
So how did our parks measure up? The average NDVI for the parks we measured was 0.38. About ⅓ of the parks scored relatively low (NDVI (<0.3), and about ¼ scored relatively high (NDVI (>0.5)) for a park.
We found much less variation across the cities we worked in – but there was still some variation in greenness, with Glendale, Burbank, and Los Angeles being more green, and Hemet, Moreno Valley, El Monte and South Gate being less green.
This result illustrates that more socio-economically disadvantaged neighborhoods are also more nature poor. It also points to cities where parks, if they were “green”, might yield the greatest benefits if they gave a boost to those cities which were least “green”.
Research Results Poster