Yosemite National Park | World Heritage Outlook (2024)

The variety of flora is reflected in the existence of six distinct vegetation zones which are governed by altitudinal variation. Notable are three groves of the giant sequoia tree and extensive alpine meadows. There are 1,200 species of flowering plant along with various other ferns, bryophytes and lichens. There is one endemic and eight threatened or endangered species of plant. The park has 67 mammalian species, of which 32 are rodents, 221 species of bird, 18 reptile, 10 amphibian and 11 fish, of which 6 are endemic (IUCN, 1984). Bighorn sheep were declared extinct in Yosemite in 1914 but were reintroduced in 1986.

Air pollution is currently recognized as one of the most significant threats to the resources of the Sierra Nevada (National Park Service, 2020a). Ozone levels are a threat to the site (Kohut 2007). Yosemite has 8-hour ozone concentrations that are consistently at or above the standard of 75 ppb. The ozone W126 index values at 28 ppm-hours during 2007. National Park Service(2009) and NPCA (2017a) say that ozone levels warrant significant concern. Yosemite also experiences haze levels well above estimated natural conditions, affecting views of iconic landmarks such as Half Dome and El Capitan (NPCA 2017a). Significant tracts of the ponderosa and Jeffrey pine trees in the park show evidence of injury by ozone (Durisco 1987, NPCA 2017a). These levels of air pollutants adversely affect the park's aesthetics. Unfortunately, Congress recently voted to delay implementation of standards aimed at reducing ozone pollution in the USA (NPCA 2017b). The issue is being contested in the courts (NPCA 2018a).

Although 94% of Yosemite is Congressionally designated wilderness, the remaining 6% has serious problems with over-development, especially in Yosemite Valley. Over a thousand buildings are crowded into one end of the 1,428 ha valley (National Park Service, 2012). There are, for example, 1,504 campsites in 18 camp grounds, 210 picnic sites in 24 picnic areas, 3 visitor centers, 6 museums and major exhibits, 2 amphitheaters, 8 Ranger stations and 6 entrance stations (National Park Service, 2012). There are 344 km of paved roads; there are 1200 buildings within the park; and over 2000 employees of theNational Park Service and hospitality industry work in the park over summer (National Park Service, 2020b). Within Yosemite Valley itself, this development has created a congested urban environment, which encroaches on the natural beauty of the valley and impacts natural ecosystems and wildlife. Park congestion therefore requires mitigation strategies (National Park Service, 2020a).

There are no current limits on the number of people that can enter the park each day. Visitor numbers to the park have stabilised at around the 4-5 million mark in recent years, with a peak of 5.2 million in 2016 (National Park Service, 2020b). Approximately three quarters are day visitors (Blotkamp et al. 2010). Private automobiles were used by 69% of all users, while 30% used rental automobiles. This number of vehicles results in serious gridlock on many summer weekends; statistics that enumerate traffic accidents, road fatalities and collisions with bears note around 25 a year (National Park Service, 2020b). With excessive visitor use, a valued resource, such as a sense of solitude, can diminish or even disappear. Overcrowding has been identified as a problem (NPCA 2018b). The park manager has identified the site's natural 'soundscape' as a characteristic worth protecting, has measured noise coming from mechanised sources and identified means of mitigating noise from artificial sources (National Park Service, 2020a). In March 2020, theNational Park Service website reported that Yosemite National Park was closed due to coronavirus (National Park Service, 2020j); while this may provide some respite for the park's assets, it does not constitute a desirableor long-term solution.

One of the most vexed issues facing park management (as it is for many of the world's large protected areas) is that of fire. On the one hand, ecologists have identified the lack of fire due to decades of deliberate suppression as a major problem (National Park Service, 2020a, Miller et al. 2012, van Wagtendonk and Lutz 2007). On the other, climate change is intensifying the extent and severity of fires, necessitating emphatic responses during the height of summer in a state that is world-renowned for savage wildfires. New policies, measures and tools have been introduced to address this threat. In 2017, theNational Park Service amended its fire-management plan with a 'community and infrastructure protection policy' aimed at increasing the organisation's flexibility in dealing with fires (National Park Service, 2020c).

Invasive species have been identified as an environmental issue affecting the site and it has implemented programs to reduce the prevalence of some of these (National Park Service, 2020a).Currently there are 177 non-native plant species in the park, of which 5 are considered invasive (National Park Service, 2012). Efforts are being taken to mitigate those 5 species, but it is estimated that additional non-native plant species will invade the park each year. There are 9 species of non-native fish in 1,939 km of streams in 2 major river systems and in 245 lakes (National Park Service, 2012). Management of invasive species has been successful but with funding in all USA national parks under pressure, the program may have difficulties in the future.

Climate change and associated alterations to the site's fire regime constitute the major potential threat. The issue has been identified by the park manager (National Park Service, 2020a) and NGOs (NPCA 2018c). A resurvey of sites first established in the 1920s indicates that climate induced changes to small mammal populations might be occurring; formerly low-elevation species expanded their ranges and high-elevation species contracted theirs, leading to changed community composition at mid- and high elevations; though some high-elevation species are threatened, protection of elevation gradients allows other species to respond via migration (Moritz et al. 2008). Climate-induced decreases in snowpack(Roche et al. 2018) and the associated increase in fire severity suggest that existing assumptions may be understated – fires may become more frequent and more severe (Lutz et al. 2009). Reduced snowpack also leads to reduced run-off and reduced volumes in waterfalls, potentially impacting on a critical part of the site's awe-inspiring scenery. Some changes identified as consistent with but not formally attributable to climate change include: higher-elevation tree shift (Dolanc et al., 2013), large tree decline, (McIntyre et al. 2015, Nesmith et al. 2018), upslope fire shift (Schwartz et al. 2015), and earlier spring (Monahan et al. 2016, Gonzalez et al. 2010b, Drexler et al. 2015), among other changes.

Currently there are only 177 non-native plant species in the park, of which 5 are considered invasive (National Park Service, 2012). Efforts are being taken to mitigate those 5 species, but it is estimated that 10 new non-native plant species occur in the park each year. Efforts are also underway to eliminate the bull frog from park waters, but this effort is not sufficiently reducing frog populations. The wild turkey appears to be spreading into the park, and no efforts are currently underway to stop its spread. There are 9 species of non-native fish in 1,939 km of streams in 2 major river systems and in 245 lakes (National Park Service, 2012). Invasive species management has been successful under current funding levels. With some funding cuts being considered, the program may have difficulties in the future.

TheNational Park Service remains an exemplary management body - one of the best in the world - thanks to dedicated staff and a strong internal culture. The management system in place is adequate to maintain the site's Outstanding Universal Value. However, it is beyond the capability of the park authority to influence off-site air pollution sources, fires entering the park from off-site, or the globally ubiquitous effects of climate change.

The park has a General Management plan approved in 1980 that requires updating, particularly when it comes to climate change and fire. In the meantime, the park authority has shown the agility necessary to adapt to changing circ*mstances by updating planning documents for particular issues, such as fire (National Park Service, 2020c). Management prescriptions vary according to the park's zoning, with the wilderness areas, for example, covered by a comprehensive set of regulations (National Park Service, 2020d).

The boundary encompasses two nearly complete watersheds and the park's shape means that its perimeter encompasses a large area. The spectacular landscapes and glacial landforms that form the essence of the site's Outstanding Universal Value are well protected by the park's boundaries (it should be noted, however, that the Hetch Hetchy valley, a spectacular part of the park, was inundated by an artificial reservoir in 1923 - a campaign to restore this part of the site continues to this day). From an ecological point of view, the boundaries could be improved by including upper parts of one of the catchments. However, because the park's eastern and northern edges abut designated wilderness areas, Yosemite forms part of an extremely well protected wider landscape of about one million ha in extent (NPS and US Department of the Interior 2020).

No information could be found on theNational Park Service website regarding the integration of park planning for Yosemite with state and municipal jurisdictions.

Although key stakeholders have been identified, they are not directly involved in site management. TheNational Park Service uses a Parkwide Programmatic Agreement as a means of furthering consultation with local native tribes and groups (National Park Service, 2020e). Indigenous hunting and gathering and spiritual ceremonies have been carried out and the park manager's relationship with indigenous people has been described as 'fair' (UNESCO 2013). Other local communities are primarily concerned about sustaining and increasing visitation to the park because their economies have grown dependent on park visitors. This leads to some conflicts with minimizing the impacts of high visitation rates.

The legal framework applying to the Yosemite National Park consists of federal laws and the park regulations set out in the Superintendent's Compendium that cover issues such as campfires, road closures, rock climbing, traffic, permits etc (National Park Service, 2020f). The site is governed by federal statutes that established the Yosemite National Park, the Yosemite Wilderness, the Tuolumne Wild and Scenic River, and Merced Wild and Scenic River. Other general federal acts cover establishment of the National Park Service, air quality, water quality, environmental policy, wild and scenic rivers, wilderness, endangered and threatened species, historic preservation, and archaeological resources protection. These statutes are generally effective in maintaining the Outstanding Universal Value of the site.

The park manager has substantial law-enforcement capabilities to protect the park's natural assets. The park employs 1,300 rangers during summer (National Park Service, 2020b) and also has the use of helicopters to help enforce the laws (NPS 2020 / Aviation Management). TheNational Park Service website has published examples of prosecution of poachers and the eradication of marijuana plantations within the park.

There have been no substantive decisions on management of the property by the Committee since inscription so this topic has not been applicable.

The long-term increase in visitor numbers (consistently over 4 million visitors pa) combined with reports of congestion and over-crowding in the Yosemite valley raise questions about the sustainability of the park's tourism industry. Visitors are encouraged to use the park's extensive public transport system, which provides access to the park's main visitor nodes (YARTS 2020), though encouraging visitors to use public transport in favour of travelling by car is challenging. Attempts are being made to reduce water consumption and solid waste, to conserve energy, and to use sustainable products. Steps have been taken to install solar collectors, a biodiesel fuel station and the addition of hybrid vehicles to the park’s fleet. The park has initiated a Zero Landfill Project to increase recycling parkwide(National Park Service, 2020g). The management of the 94% of the park that is designated wilderness is effectively carried out through a permit system and associated regulations (National Park Service, 2020d).

The 2019 operating budget for the park was 29 million USD, providing for a workforce of 800 employees in summer and 478 in winter (National Park Service, 2020b). Additional funding for specific projects is available through a friends association. NGOs frequently express alarm and frustration about proposed and/or actual budget cuts on all parks (NPCA 2019); at Yosemite, one report in 2017 identified a $582 million backlog in maintenance of park infrastructure (Bachmann, 2018). Given the requirement of theNational Park Service to service the needs of the 4 million visitors per annum, it is not clear whether the park's funding is sufficient to maintain the property's Outstanding Universal Value over the long term.

Staffing levels and capacity of the USANational Park Service have been adversely in recent years (many reports online, such as Koebler 2017,Repanshek 2017 and Bachmann 2018). The regular deadlocks in Congress over the federal budget have also been disruptive. Spokespeople for theNational Park Service have reported there to be enough staff to successfully manage the property (Bachmann 2018), although civil societies have expressed their serious concerns for the impacts of budget cuts on staffing levels of all parks (NPCA 2019). The National Park Service, however, has a strong internal culture of dedication to national parks and, by world standards, the staff capacity, training and development remain good.

TheNational Park Service has an excellent program of interpretation and education about Yosemite that can be accessed online (National Park Service, 2020h), in brochures, in visitor centres, and on the trails.

Overcrowding and congestion are common in the Yosemite Valley. Despite the problems, the visitor numbers remain on an upward trajectory, with up to five million park visitors per annum. Impacts include additional pollution in the park, noise and the loss of seclusion and tranquillity. TheNational Park Service promotes the park's excellent bus-transport system (YARTS, 2020) and has taken other measures to reduce the impacts of over-crowding (National Park Service, 2020g). The 94% of the park designated as wilderness has an effective system of permits and policies (National Park Service, 2020d). In March 2020, the park website Yosemite National Park was closed due to COVID-19, but has subsequntly re-opened.

The park manager systematically monitors visitor impacts and water values associated with its officially designated wild and scenic rivers (NPS 2020 / Visitor Use and Impact Monitoring Program [online]). Characteristics that are regularly measured include informal trails, the amount of bare soil within meadows, landscape, hydrology, and physical and biotic structures. The results of monitoring trigger management actions that include increased monitoring, secondary measurements and studies, visitor education and outreach, and ecological restoration. Additional monitoring pertains to birds, fire ecology, air quality (including smoke levels), invasive plants and various forms of visitor activity.

There are over 100 staff carrying out resource management and scientific research (National Park Service, 2020i). The park serves as a public meeting place for scientific symposiums, with topics including fire science, hydro-climatology, archeology, and bird surveys, with scientific papers presented at the monthly Yosemite Forum. The park also processes hundreds of research permits every year for its staff and outside interests. The park sponsors a park-based social science branch, which serves as a model for work in visitor use and user capacity issues. Particular areas of research include flora, fauna and snowpack. The park manager administers the Yosemite Research Library, a specialized library focusing on human and natural history.

Some Concern

High Concern

The 302,881 ha Park, of which 94% is federally designated wilderness, includes two relatively pristine watersheds. These watersheds make a significant contribution to the water supplies of the San Francisco Bay area and the cities and irrigation districts of California’s central valley. However, the reservoirs that store this water are an intrusion upon the park's natural characteristics and if alternative means of utilising these catchments' water resources were implemented, a landmark example of environmental restoration could occur.

Recent droughts reduced water quantity and quality. There is concern that global warming will exacerbate drought conditions affecting all species in the future.

Yosemite has been home to Native Americans for millennia. It encompasses sacred sites and landscapes and continues to be part of their spiritual heritage. In addition, the park is an outstanding area for contemplative reflection, one of the most important values of a protected area. Yosemite Valley and the Wilderness that surrounds it are among the world’s most evocative scenery.

As the over 4 million visitors per year can attest, Yosemite is extremely important for recreation and tourism. It is a major destination for travellers from California, the US, and the world. It contributes substantially to the local and regional economy.

The relatively pristine ecosystems of Yosemite represent an outstanding opportunity to advance society’s understanding of ecological processes and functions. The opportunity to study the ecological role of fire in an area where lightning ignitions can burn under prescribed conditions is very rare in temperate zones. The great exposure of geological formations and land forms make Yosemite a destination for earth scientists to better understand the processes that shape the landscape.

Impacts of roads and other small-scale exploitation in the Yosemite valley detract from the scientific value of this part of the site.

The vast expanses and ranges of elevations in the park make it ideal for climate change mitigation and impact amelioration. The fire program has been successful shifting biomass from smaller trees to larger trees, thereby contributing to carbon sequestration.

There is a concern that climate change could cause large tree decline limiting carbon sequestration, altering biological diversity and exacerbating the spread of invasive species (Gonzalez et al. 2010b, Bradley et al. 2009).

2014 cumulative benefits to local communities were estimated at $535 million USD, supporting 6,261 jobs.