Urban and community forests are of great value in the Great Plains. To the 66% (1.2 million) of Nebraskans who live in urban, suburban and community areas, trees provide many goods and services. An urban or community forest refers to the collection of trees, shrubs and related vegetation growing in cities and towns. These areas include city parks, streetscapes and trees on public, private and commercial lands. In Nebraska there are approximately 470,000 acres of community forests (NFS, 2007). A large and diverse number of tree species are found in the community forest with the typical forest resource being dominated by hackberry, red mulberry, Siberian elm, juniper (Juniperus spp.), elm, ash and mixed hardwood and evergreen species. In Lincoln and Omaha, the state's two largest cities, the most common species are Siberian elm, hackberry, eastern redcedar, ash, red mulberry, Scotch pine and mixed hardwood species. This "green infrastructure" provides many valuable benefits important to human and ecological health (Nowak and Greenfield, 2010) including:
- storing 1.5 million tons of carbon, at a value of $31.9 million;
- sequestering 50,706 tons of carbon/ year, at a value of $1 million;
- removing 1,146 tons of total pollutants/ year, at a value of $8.4 million;
- 20 tons of carbon monoxide/year (value of $24,600);
- 205 tons of nitrogen dioxide/year (value of $1.8 million);
- 440 tons of ozone/year (value of $4 million);
- 68 tons of sulfur dioxide/year (value of $150,200);
- 410 tons of particulate matter/year (value of $2.5 million);
Other measurable benefits of Nebraska's urban and community forest resource include:
- surface air temperature reduction;
- increased energy efficiency and reduced fossil fuels use;
- absorption of ultraviolet radiation;
- improved water quality;
- reduced noise pollution;
- improved human comfort, health and psychological well being;
- increased property values;
- provision of wildlife habitat;
- improved aesthetics; and
- improved community cohesion.
There are 503 Nebraska municipalities (League of Nebraska Municipalities, 2009). Based on 2010 U.S. Census data, Nebraska has a population of 1,826,341, with three- quarters residing in the eastern third of the state (U.S. Census, 2011; Nebraska Blue Book, 2009). Two-thirds of the population lives within communities that have a population of 2,500 or more people (Nebraska Blue Book, 2009). The trees and forests in all Nebraska communities provide a range of enormously valuable environmental, social and economic benefits. On average, every dollar invested in the community forest resource returns an average of $2.70 in net annual benefits over the lifespan of a publicly owned municipal tree (McPherson et al., 2005).
NFS's Community Forestry & Sustainable Landscape program annually cooperates with more than 140 communities. One of the cornerstones of this program effort is the national Tree City USA program sponsored by the Arbor Day Foundation and administered statewide by NFS. Participating communities must meet four standards set by the Arbor Day Foundation including:
1. Existing tree board or department.
2. Established tree care ordinance.
3. Community forestry program with an annual budget of at least $2 per capita.
4. Arbor Day observation and proclamation.
Begun in 1976, the Tree City USA program has grown in Nebraska to involve the annual certification of more than 100 communities representing more than 66% of the state's population. These communities annually invest more than $5 million in the care and management of local community forest resources with an average per capita expenditure of $4.93.
In 2010, NFS inventories and calculations using UFORE (Urban Forest Effects Model) estimated that there were approximately 13.3 million trees in Nebraska communities. Collectively, the community forests of Nebraska have an average tree cover of 11.3% with a total value of environmental, social and economic benefits to the state of $9.7 billion.
A 2010 UFORE analysis of Lincoln and Omaha, which collectively represent approximately 40% of the state's 1.79 million residents, determined there are more than 5.4 million trees in the two cities. These trees provide $20.1 million worth of carbon storage, $747,200/year of carbon sequestration and have a structural value of $3.98 billion.
The extent of Nebraska's urban and community forest resources have steadily declined in recent years. A combination of severe weather events (1991 freeze, 1997 snow storm, 2007 ice storm, tornadoes and high winds), chronic drought, poor planting practices, poor species selection, insect and disease pests and a preponderance of older trees nearing or past their average life span have severely reduced the number of trees in communities across the state. Trends gleaned from more than 200 community tree inventories conducted by NFS since 1977 indicate that the state has lost approximately 50% of its urban and community forest resource since the late 1970s (NFS, 2007).
Nebraska's urban and community forest resource faces additional threats. Various insects and diseases, with the potential to kill trees and reduce the health, value and sustainability of local tree resources, are either present in or rapidly approaching Nebraska. Of particular concern to Nebraska community forest resources are Asian longhorned beetle, gypsy moth (Lymantria dispar), Dutch elm disease and EAB. If it becomes established in Nebraska, Asian longhorned beetle, an insect that bores into and kills a wide range of hardwood species, could generate $3.35 billion in losses in structural value to the state's community forest resource. Asian longhorned beetle's potential impacts on Omaha and Lincoln alone are $1.2 billion and $219 million respectively. Gypsy moth, which feeds on many tree species causing widespread defoliation and tree death if outbreak conditions last several years, could generate $2.13 billion in losses in structural value statewide. Gypsy moth's potential impacts on Omaha and Lincoln are $566 million and $324 million respectively.
Dutch elm disease has been present in the United States. since the 1930s and devastated much of Nebraska's community forest resource during the 1960s and 1970s. Statewide this disease continues having the potential to cause $423 million in losses in structural value to the state's native elm population and $116 million and $40 million within Omaha and Lincoln respectively.
EAB has killed tens of millions of ash trees in the upper Midwest and is the most serious known threat to the urban and community forest resources across the state. EAB could generate $823 million in losses in structural value statewide and $192 million and $89 million within Omaha and Lincoln respectively.
Collectively, these insect and disease pests threaten more than 8 million trees in urban and community landscapes across the state and represent potential structural value losses of $6.7 billion.
- Dramatic decline in community forest cover over past 30 years.
- Inadequate species and age diversity to sustain the urban and community forest resource.
- 66% of population lives in cities and towns with 470,000 acres of community forest.
- High concentration of green ash, black walnut and Scotch pine, at risk to EAB, thousand cankers disease, and pine wilt, respectively.
- Declining urban and community forest cover reduces mitigation of harsh climatic conditions in the Great Plains.
- Declining ability to mitigate climate change impacts (temperature, wind, air quality).
- Risk of losses from attack by invasive species due to high value of trees in urban areas and the ecosystem services and economic benefits provided.
- Some communities have greater community forestry assistance needs than others.
Multistate Priority Areas: Due to their proximity to adjacent states, Omaha is a multistate priority forest area with Iowa, and South Sioux City is a multistate priority area with South Dakota and Iowa.
This information is from the Nebraska Forest Service Statewide Assessment and Strategy. To view this document go to: nfs.unl.edu or click here and go to page 69 within the document.