What are Tiny Forests?
The concept of the Tiny Forest method of habitat restoration originates with Akira Miyawaki, a Japanese botanist and plant ecologist who pioneered the movement after being inspired by the forests around Shinto shrines. It has been replicated many times around the world, perhaps most famously by Shubhendu Sharma, an industrial engineer turned eco-entrepreneur who has helped grow more than 140 of these Tiny Forests.
The goal of a Tiny Forest is simple; take a barren plot of land and turn it into a diverse community of plants that resembles a natural forest. That goal matches that of many other afforestation and forest restoration projects, but the Tiny Forest method touts some key advantages for cities in particular: faster growth, higher biodiversity, and less maintenance than more traditional landscaping. The following are some of the features that differentiate a Tiny Forest from other landscaping projects.
Diversity of Native Plant Species
A Tiny Forest aims to have at least 30 native plant species, representing a mix of trees and shrubs that are indigenous to the area. In general, the greater the diversity of native plants and habitat structure, the greater diversity of wildlife that the forest will support. We emphasize native plants for two reasons; (1) they are adapted to the local climate and (2) they tend to support more native wildlife than non-native or exotic plants. Due to our semi-arid climate in the Lower Rio Grande Valley of Texas, the drought-resistance many native plants exhibit is particularly important.
Flexible Size and Location
Typically, Tiny Forests range in size from the size of a tennis court (about 0.05 acres or 2,150 sq. feet) to 3/4ths of a football field (about 1 acre). They can also be arranged in a a variety of shapes. This flexibility allows a Tiny Forest to complement other land uses in cities and be tailored to specific sites, such as school yards or city parks.
Thorough Site Preparation
Removing invasive species and other barriers to a Tiny Forest’s establishment and growth (such as compacted soils and/or nutritionally deficient soils) is important for success. Site preparation can include removal of existing invasive vegetation, loosening soils (disking or tilling), and adding soil amendments as needed (such as compost).
Dense Plantings
A significant difference between Tiny Forests and other methods is the density of plantings (or the number of plants installed per unit area). Tiny Forests aim to have 2-3 plants per square meter (roughly equivalent to 2-3 plants per 11 sq. feet). This high density planting helps the forest resist invasive species and can encourage quicker growth through competition for space, light, and water, as well as mutualisms.
Thick Layer of Mulch
Mulching around the planted trees and shrubs helps to retain soil moisture, which, especially in arid climates, is very important for forest establishment. Mulch also hinders growth of invasive grass species and adds nutrients to the soil as it gets broken down by fungi and other decomposers over time.
Early Care
Watering, weeding, and providing other care for the Tiny Forest over the first 1-2 years gives the trees and shrubs every chance to establish healthy roots and grow. After that, the Tiny Forest can mostly be left on its own, reliant on natural rain cycles and other ecosystem processes as the plants grow, reproduce, and compete for space.
Community Involvement & Education
Because Tiny Forests are mostly planted in urban areas, they are highly visible to people. Signage, landscaping nodes, and maintained edges are some of the ways that a Tiny Forest can be clearly designated as a purposeful space. Involving schools, community centers, and other groups is vital to making sure the Tiny Forest is not only successful, but also serves as a form of educational outreach about the benefits of urban forests. Interpretive signage is an easy way to address frequently asked questions and add an educational component.
A Pilot Project at Quinta Mazatlan
The Center for Urban Ecology decided to put the Tiny Forest method into practice at Quinta Mazatlan in McAllen, Texas. We selected a 10,000 sq. foot plot (0.22 acres) with sparse tree cover as our site. Most of the existing trees are scattered Honey Mesquite (Prosopis glandulosa), Texas Ebony (Ebenopsis ebano), and Anacahuita (Cordia boissieri) with few shrubs or small trees in the midstory layer. The herbaceous layer was dominated by Guinea Grass (Megathyrsus maximus) and Buffelgrass (Cenchrus ciliaris), and was the first challenge as we started preparing the site for restoration.
To combat the invasive grasses, we mowed as much as we could around the existing trees and followed that by spreading silage tarps over a large swath of the plot for soil occultation. By leaving these tarps over the mown plot, the invasive grasses were deprived of all light (unable to photosynthesize) and experienced elevated temperatures (especially in the summer heat). We left our tarps on for six weeks during the summer of 2021. When we removed the tarps, the dead grass had created a thick layer of straw mulch – prior to mowing, the grass had been about four feet tall. We then cleared the areas that could not be mown or tarped via manual control methods (shovels, hand weeder tools, and rakes).
We planted 850 native trees, shrubs, and forbs in the fall and winter of 2021, concentrating most of the plantings in open areas with little-to-no existing tree cover. We selected species that are found in a variety of forest habitats in the Lower Rio Grande Valley, including fast- and slow-growing species, early successional and climax species, and sun-loving and shade-tolerant species. We planted at a density of 2 plants per sq. meter (or 2 plants per 11 sq. feet) randomly dispersed through the area. We then watered all the transplants thoroughly and mulched any areas that did not have a thick straw mulch from the silage tarps.
Over the subsequent months since planting, we have continued to periodically water and weed the Tiny Forest. Thanks to our thorough site preparation and thick layer of straw mulch, we have had very few invasive grasses growing in the plot so far – those that do are easily removed by hand before they mature enough to go to seed. We will continue to care for and monitor the progress of this Tiny Forest for the next 1-2 years and use what we learn to inform future projects. We hope you will come visit it!
The Benefits of Urban Forests
The burgeoning field of urban ecology highlights the benefits of supporting healthy trees and forests in the places we live, work, and play. These benefits are often labeled as ecosystem services, or simply the benefits that people derive from ecosystems and their components. A growing number of scientific research projects and case studies explore the links between urban forests and the benefits they produce for people and wildlife. Here in the Lower Rio Grande Valley, there are key issues that healthy urban forests could help address in our rapidly developing region.
Cooling Cities
The Urban Heat Island Effect is the phenomenon of how cities tend to be warmer than their surrounding exurban or rural landscapes. This warming is driven by the removal of existing natural land cover (forests, wetlands, grasslands) and replacing them with built landscapes of asphalt, pavement, buildings, and other structures that absorb and retain heat. On average, urban heat islands can be 5-7 °F warmer than their surrounding rural areas, and single-day temperatures sometimes up to 27°F more. Trees can help mitigate this effect through shading and evapotranspiration. As a result, areas with more trees are cooler, leading to more comfortable environments, and help reduce electricity use and lower energy bills. This is especially important during heat waves.
Stormwater Management
Another impact of the impervious surfaces that contribute to urban heat is that they also prevent stormwater from infiltrating soil. During rain events this means that there is a sudden influx of stormwater into city water systems and can lead to greater likelihood of flooding. How urban forests help is by intercepting rain with their canopies, which slows the flow of water to the ground (or may just linger on the tree until evaporation). Once the rainwater reaches the ground, tree roots provide pathways for that water to infiltrate the soil. Urban forests also help reduce water pollution by limiting how much water flows over commonly polluted areas, such as parking lots and streets, and carries those pollutants into water treatment systems. In essence, having an urban forests slows down the flow of water during rain events, flattening the sudden spike of water entering city systems and reducing the chance and severity of flooding.
Community Health and Well-Being
Both reducing heat and mitigating flooding have positive impacts on human health, and yet urban forests offer far more health and wellness benefits than that. Trees remove air pollution, reducing respiratory diseases – one study found that children that live in areas with more trees have lower prevalence of asthma. Because urban forests make cities more pleasant to experience the outdoors, they also lead to more active lifestyles and the associated health benefits. Being around forests and green spaces also alleviates stress, lowers anxiety, and helps reduce ADHD symptoms.
A Call to Action
All of the ecosystem services mentioned above lead to a basic conclusion: by planting more trees, whether by creating Tiny Forests or in combination with other tree-planting efforts, we can enhance livability, well-being, and resilience in our cities. We wouldn’t be alone in those efforts; cities around the country are putting together plans to increase their tree cover as well, recognizing the value of healthy urban forests.
One of the first steps towards creating a plan of action is to assess where we stand (pun intended) in regards to our urban forests. We conducted our assessments for the largest cities in the McAllen metropolitan area (Edinburg, McAllen, Mission, and Pharr) by using i-Tree, a program developed by the the USDA Forest Service. Using Google Maps imagery, the program randomly selects points for the user to designate as different land covers; grass/herbaceous, impervious (buildings, roads, other), soil/bare ground, tree/shrub, and water. The more points that are classified, the more the accurate the results. The program also generates a monetary value of the benefits the trees provide the selected area.
What We Found
The McAllen metropolitan area had an average tree canopy cover of 16.4%, which translates to roughly 26 square miles (out of 160 square miles). Those trees provide an estimated $7,690,000 in air pollution removal, avoided water runoff, and carbon sequestration benefits annually, plus represent an additional $99,230,000 in already-stored carbon. We then used publicly available data to compare how our tree canopy cover compares with other areas. Our average tree cover of 16.4% is below both the Texas urban community average (28.3%) and the US urban community average (42.2%).
While there is no set amount of tree canopy cover a city should have – climate pays a role (cities in deserts, for example, tend to have less canopy coverage than more temperate cities) – there is certainly room for the Lower Rio Grande Valley’s urban forests to grow and provide even more benefits for people and wildlife. In the same i-Tree Canopy assessments, we found that roughly 58 square miles of land in Edinburg-McAllen-Mission-Pharr were covered by grass or other low-growing herbaceous plants. These are areas such as lawns, city parks, school yards, and vacant fields where there is ample room to add trees.
For us, we see a green future for the region, filled with urban forests that provide us shade, beautify our spaces, help reduce flooding, and support a diversity of birds, butterflies, and other wildlife that maintain our ecosystems and draw eco-tourists to the region. We see healthy people and smart development. It’s time to grow.
Center for Urban Ecology 
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