How much do you think you could learn from a patch of rock the size of a doormat? Maybe you’d take a snapshot of the plants growing on the surface, the little critters sitting on it, and the material of the rock itself. But how much could you learn if you took that same snapshot 30 years in a row?

The NPS Mediterranean Network Inventory & Monitoring team in Southern California has done exactly that, imaging multiple doormat-sized locations in Cabrillo National Monument over three decades and building massive data sets to better document and understand the species in our natural spaces.

Back in 1990, marine ecologists working at the park set up fifteen monitoring locations in the Cabrillo tide pools and took pictures of the species living in each location. They returned the following year, and the year after that, and so on, taking pictures of the same 15 locations all the way up to the present year, 2022, while simultaneously logging the percent of each type of species taking up space on the rock.

This long-term monitoring data was compiled into visually stunning graphs, which display the spatial changes of the proportions of each species over the years.

Understand the Data | This specific plot shows us the concerningly sharp decline in mussel population (in black) during the first few years of monitoring. Mussels are what marine ecologists consider a “foundation” species: their presence in an ecosystem creates habitat and shelter for many other species. Mussels grow in dense aggregations, or mussel beds, which are often used as shelter by small marine flora and fauna. Decline of mussel populations may result in other species taking their place without providing the same amount of habitat, which could significantly diminish biodiversity within the ecosystem.

In this location, the mussel density did not recover after the initial drop that all the species experienced, but other organisms, like various seaweed and barnacle species, rebounded quickly into the new space, slowly spreading in the following years to take up more of the rocky real estate. Because this data is collected in the wild, and not in controlled laboratory settings, there are almost infinite reasons to explain these abrupt and startling population changes. NPS ecologists have come up with over 20 possible hypotheses for these changes, including a warmer tide pool climate that has been shown to be particularly dangerous to younger mussels, less food availability in local waters, and human usage of the area, all of which may be preventing the growth of large, healthy, adult mussel populations.

Ever wondered what our national parks looked like 200 years ago? The flourishing ecosystems we see in our protected spaces today is the collective work of scientists, conservationists, and public service officials from local, state, and federal organizations. In the Channel Islands of Southern California, it was these continued, concentrated efforts over decades that are only just beginning to rectify some of the damage of human settlement and invasive species, and to restore the delicate ecosystems that make these islands so notoriously beautiful, diverse, and intriguing.

Protected long-term rest and recovery are crucial for the restoration of healthy ecosystems in our national parks. Park management makes evidence-backed decisions about how to best protect and support native plants and wildlife, while scientists from the National Park Service and its partners, including the U.S. Geological Survey, monitor long-term changes in local flora and fauna, changes that could be caused by climatic perturbations, increased visitor use, the introduction of invasive species, etc.

Such monitoring programs are akin to a medical doctor regularly checking a patient's pulse as an indicator of change in health. In the case of Southern California’s Channel Islands National Park, the park’s decision to remove introduced grazers, like pigs, cattle, deer, and elk, brought about a remarkable recovery of ecologically important native plants, including that of the beautiful, endangered Arctostaphylos confertiflora, the Santa Rosa Island manzanita (left).

The Santa Rosa Island manzanita is one of the many island species that has been carefully monitored and protected during its recovery from the ranching era of the Channel Islands. The ranching era, beginning in the early 1800s and continuing through the late 1900s, consisted of individuals with land grants setting up ranching infrastructure on the islands, which included bringing and raising large numbers of livestock and game animals. With a plethora of wild grasses and no natural predators, these grazers grew to massive population sizes and brought about some of the most troubling and long-lasting changes to vegetation biodiversity on the Channel Islands.

By the time the islands became protected spaces under the NPS, park management and ecologists were already aware of the concerning impacts of excessive grazing, and how it had upset the natural balance of the islands’ ecosystems. Researchers at NPS and USGS immediately put long-term monitoring plans into action, specifically to document ecosystem recovery. Islands are a unique resource in which to observe ecosystem changes, and learning about recovery in these controlled and isolated contexts can offer valuable insights for future restoration projects. Today, nearly 100 species of plants within the park are considered uncommon, rare, or at risk of decline, and 14 are federally listed as endangered or threatened species, making this project incredibly important.

As part of the efforts to understand and demonstrate the recovery of the Channel Islands’ ecosystems, NPS ecologists started tracking the amount (specifically, percent cover, which is a measure of relative abundance) of multiple species of plants, including the endangered Santa Rosa Island manzanita that comprises an integral part of the island's chaparral habitat.

Understand the Data | This figure shows the percent cover of manzanita averaged across all monitoring sites that contain the species on Santa Rosa Island over the last three decades. For example, in 2012, the percent cover of manzanita was registered at 16% of the total points (100 points per site) measured on the island.

This species plays many important roles in the island’s ecology, one being growing berries that are a favorite of Urocyon littoralis, the endemic island fox that roams several of the Channel Islands (left). 

In the 1990s on Santa Rosa Island, NPS began a grazer removal program in earnest, as an attempt to begin to restore native vegetation. All livestock cattle were removed at once, but, as the graph shows, there was no immediately noticeable change in manzanita recovery after cattle removal. Gradual but substantial removal of elk and deer followed into the early 2010s until their full elimination from the island by 2015. A few years after the last deer and elk removal, manzanita plants were finally able to produce flowers and seeds once again–the grazers had been eating them for more than a century. The monitoring data show an exponential increase in the percent cover of manzanita, because as the photo clearly demonstrates, their canopies cover more ground.

Continued monitoring will track population changes as seedlings sprout from the new seed bank.

The long-term approach to monitoring the vegetation after the grazer removal decision was extremely important. Strong observational evidence indicates that the rapid decline of much of the Channel Islands’ rare vegetation was due to the sudden introduction of multiple species of herbivores, particularly those without natural predators roaming the islands to keep population sizes in check.

As the previous bar chart shows, even with as significant a change as the instantaneous removal of all cattle from Santa Rosa Island, there is relatively little recovery in manzanita abundance in the years immediately following grazer removal. But the difference and importance of this choice becomes obvious within two decades, with overwhelming growth of happy, healthy native vegetation - one that would not have been possible if the management choice had been reversed due to the lack of immediate recovery in the first few years.

They say that a picture is worth a thousand words, but scientists might tell you that it’s worth a thousand data points. While long-term monitoring data can provide park management with deeper perspectives on natural systems, a snapshot of an ecosystem can provide timely insights into ecological change.

Using one of these “ecological snapshots,” researchers at the National Park Service and the U.S. Geological Survey found that biodiversity–the number and variety of species in an area–can continue to exist even as the living area gets smaller. This has surprising implications for maintaining biodiversity in urbanized spaces: small, protected, healthy habitats in human-dominated areas can still uphold healthy biodiversity within their ecosystem, even though the ratios of species may not be exactly reflective of the native habitat’s distribution. 

NPS and USGS scientists wanted to learn more about how biodiversity within a herptile (reptiles and amphibians) ecosystem may be impacted by habitat size, but counting every single individual of each and every species over multiple decades was an impractical plan. Instead, these scientists decided to work within multiple, small patches of land, taking “species snapshots” to measure biodiversity and observe ecological balance.

To observe the effects of habitat size on herptile populations, capture zones were set up in and around the Santa Monica Mountains and Simi Hills to see the location and abundance of the different species in each area. Zones labeled “C” were core zones, and were most representative of the native habitat and “normal” biodiversity, before human urbanization of the area began to reduce habitat area. Zones labeled “S” were small zones, and “L” were large zones. Small zones represented areas experiencing the greatest human impact on the lizards’ natural habitat size, whereas larger zones experienced moderate impact, between that of small and core zones.

Understand the Data | This figure focuses on two species -

The graph shows the relative abundance of each in differently-sized zones of capture. Core zones and large zones had, on average, a larger ratio of SCOC lizards to UTST lizards, respectively. Small zones had a variety of ratios, but overall, significantly higher ratios of UTST lizards to SCOC lizards

Understand the Data | This figure shows the relative biodiversity (Shannon Diversity Index: H’) of all the species captured within each of the small, large, and core zones. An H’ value equal to or greater than 0 indicates greater relative biodiversity, meaning a larger number of overall species.

The core zones, which were the largest capture zones and the least affected by urban development, had the greatest relative biodiversity (>1.5 H’). S4, a small zone in the city that was mostly devoid of the original habitat, with lots of bare ground and non-native grasses, had the lowest biodiversity.

Large zones had slightly less biodiversity than core zones, and small zones had less than large zones, but, overall, even in the small zones, biodiversity remained relatively high.

While the second figure shows us that overall biodiversity can be maintained even in smaller habitats, possibly even on par with larger, pre-existing natural habitats, the first figure suggests that increased urbanization and destruction of natural habitat can significantly affect ecological balances of biodiversity.

We can see how more urbanized areas have far more UTST lizards than SCOC lizards compared to the ratios in more “normal” environments. This is likely because some species are better adapted for urban landscapes while others struggle to survive, and this rapid imbalance can have unexpected, long-term consequences for the health of the entire ecosystem that the lizards are a part of.

This “snapshot” of the species roaming the Santa Monica Mountains and Simi Hills elucidates both the resilience and the sensitivity of these ecosystems to decreased habitat size and urbanization. Biodiversity remains high, with a multitude of species surviving, sharing, and interacting, even within smaller areas, suggesting that urbanized areas can still host diverse, ecologically-rich spaces.