Course:CONS200/2023/Management strategies to remove invasive blackberry in Pacific Spirit Park

The biology of the Himalayan blackberry allows for its vigorous growth in temperate, moist environments, making it invasive in the Pacific Northwest and threatening ecosystems in southwestern British Columbia . It negatively affects native BC species in various ways such as shading low-growing vegetation and limiting the movement of larger animals. As it outcompetes the native plant species, extensive local root systems are lost, increasing erosion and flooding . Patterns of invasive plant species occurrence have been discovered to correlate to the socioeconomic variable of the green spaces in the lower mainland, hence strategic management is needed . Multiple methods have been developed in order to manage its spread, including manual/mechanical methods, prescribed burning, chemical control, shading/managerial control, etc. . The Pacific Spirit Regional Park (PSRP) is a 763-hectare preserved forest area established in 1989 under the Metro Vancouver Regional Parks . The Pacific Spirit Park Society (PSPS) is a park association officially incorporated in 1998 under the Metro Metro Vancouver Regional Park Partnership program . It is a community of staff and volunteer members who run public education and stewardship programs such as EcoTEAM which removes invasive plants and plants native ones; EcoWATCH which conducts invasive plant mapping and native vs. invasive plant spread monitoring .

Himalayan blackberry species

Himalayan Blackberry (Rubus armeniacus)

Plant Features

Leaves of the himalayan blackberry shrub (Rubus armeniacus) are considered deciduous to semi-evergreen. They are palmately compound, ovate to suborbiculate, rounded base to shallowly cordate, acute or scuminate to short-attunate apex, and are unlobed. The leaf margins are moderate to coarse serrate, and have bearing hooked prickles on the largest veins. Flowers are produced in perfect clusters of 10-60, 10-15mm in diameter, with five obovate or elliptic to orbiculate petals. Flowers are mostly white or dark pink. Each flower produces aggregates 1.2 to 2 cm in diameter of 15-40 droplets (not berries). The immature fruits are hard and reddish and become dark purple upon ripening.

Growth Features

The relatively fast-growing shrub generally persists for two years, and year one develops most of the non-flowering vegetation (primocanes) and vigorous rooting. In year two of growth, vegetation grows from the first year primocanes, producing new flowers from May to August, fruits from midsummer to Autumn, then dies back. In the full life span of the Himalayan BlackBerry, stem thickness grows to 5-55mm, it's upright stems reach up to 3m in height, while the trailing stems grow to a length of 6-12m.

Habitat Preference

Himalayan Blackberry prefer climates with an average annual precipitation of 75 cm but can also grow in arid regions, such as 654 m in elevation in British Columbia. Gaire notes the moisture regime of wet winters and springs with dry summers is conforming with similar mediterranean climates also invaded by this species, such as eastern Australia, Chile, and Europe.

Himalayan BlackBerry can grow in a wide variety of soils and substratum. This species can grow in acidic to neutral soils, with textures of clay, loamy sand, and gravelly. Gaire adds that the species also has some tolerance to flooding. This wide range of tolerance for soil regimes gives the species a competitive advantage.

"In British Columbia, Himalayan blackberry occurs within Coastal Douglas Fir, Interior Cedar-Hemlock and Coastal Western Hemlock Biogeoclimatic Zones, but is most widespread in the Coastal Western Hemlock zone".

Invasive Attributes

In urban areas, invasive species are most often found in greenspaces (i.e. Pacific Spirit Park). Common explanatory variables that drive species occurrence are climate, ecological characteristics, and topography. However, the introduction and spread of a species from human interference plays a major role in species occurrence, especially in urban areas. As a result, anthropogenic, socio-economic, and land-use characteristics help us understand species occurrence.

Management strategies

Many methods of dealing with invasive plants have been developed as technology evolves and knowledge on the effects of these species grows. Typically, general management methods involve biological, chemical, or manual methods of control.

Due to their impenetrability and their range of reproductive strategies, large stands of Himalayan blackberry (HBB) are challenging to handle. However, infested regions can be transformed back into desirable levels of vegetation with the right management . Controlling HBB has become a top priority of many municipalities, and a multitude of methods of control have been developed .

Typically broken up into a two-phase process, tackling the invasive species involves removing the overground vegetation and destroying the roots and major side roots (this can be done in any order) .

The effectiveness of these strategies has been categorized by Metro Vancouver and the Invasive Species Council of Metro Vancouver.

A group of young volunteers works together to help clear out a patch of invasive Himalayan Blackberry. This picture was presumably taken in the Metro Vancouver area.

Most Effective/Recommended Methods:

Manual and Mechanical Methods of Control

• Hand pulling: Works best for seedlings/young plants
• Digging/grubbing: Basis for most manual removal projects. Requires digging out major roots and root crowns for this method to be effective. Time intensive and must be thorough, but provides the most long-term control.
• Cutting: Can be done with manually operated tools, and removes most of the aboveground portion of the plant for easy access to the roots for further control. This is a good starting step for most removal methods. Most be done repeatedly over the course of multiple years for full effectiveness, and requires high financial investment.
• Mechanical methods: Although non-selective and situationally dependent, control using mechanized equipment is highly effective and typically inexpensive. Equipment may not be safe to operate on certain slopes/landscapes, and may be receptive to certain types of soils.

Chemical Control

Metro Vancouver states that “Health Canada evaluates and approves chemical pest control products as per the Pest Control Products Act.”

• Herbicides can be applied either broadly or in spot treatments in order to deal with HBB, but both methods have their pros and cons.
• Broadcast application: Effective for dense infestations and if large patches need to be killed prior to burning, and can help stop the spread of new plants that resprout after initial removal. Timing for when these herbicides are applied is essential for the most effective treatment.
• Spot treatment: Most effective when the total area that needs to be treated is low. Three methods of spot treatment have been reviewed upon HBB and proven to be effective: spraying isolated clumps of mature HBB, spraying sprouted stems after initial removal, and treating root crowns after cutting.
• Note: companies and practitioners must be certified applicators and hold valid Pesticide Licenses in order to apply herbicide, as well as be the land manager, or gain approval from the land manager.

Partially Recommended Methods:

Cultural Control

• Closed canopy/shading: Growing a closed canopy with shade-tolerant species can help prevent HBB, as the invasive species is generally shade-intolerant. However, this is not always effective in practice due to restrictions on where tree canopy can be appropriately grown. Additionally, most patches of HBB grow along the edges of natural corridors that will always receive light, regardless of how dense the surrounding canopy cover may be.
• Prescribed/targeted grazing: Although complete removal is highly unlikely, grazing by animals can prevent re-growth if continued for long enough. This can be used as part of a larger management plan, but is not an effective removal strategy on its own. Research has shown that sheep, cattle, and horses can reduce the number of daughter plants produced significantly. However, this method is not suitable for urban areas/areas near urban sites.

Ineffective/Unavailable Methods:

Biological Control

• As of yet, there are no biological control agents or herbivorous insects that have been approved for use upon HBB. Any species that have been tested so far have posed a potential risk to other blackberry (Rubus) populations as well. Research is still being conducted on this method.

Pacific Spirit Regional Park

Geographical Location

Initially a part of the University Endowment Lands (UEL), the Pacific Spirit Regional Park (PSRP) is located on the traditional, ancestral, and unceded territory of the Musqueam First Nation. The park is a 763-hectare preserved forest area established in 1989 under the Metro Vancouver Regional Parks . Located mainly under W 16th Avenue in the Point Grey neighbourhood and around the UBC Vancouver campus, it is transit-accessible and offers over 50 km of trails for public recreation .

The Pacific Spirit Regional Park (PSRP) shown on Google Maps in reference to the surrounding areas of the Metro Vancouver Area.

Ecological Context

The park has a relatively gentle topography and is located in the maritime Coastal Western Hemlock zone according to the provincial Biogeoclimatic Ecosystem Classification system, meaning its summers are dry and warm while winters are wet and cool . The park has many evergreen and deciduous trees, bushes, ferns, mosses, fungi, and lichens that are typical of the western temperate rainforest . In terms of fauna, the park is inhabited by bald eagles, chickadees, coyotes, skunks, raccoons, and a variety of amphibians .

Human Activities

The PSRP is highly valued in its recreational ecosystem services with over 50 km of forest trails and popular attractions such as the Camosun Bog, Wreck Beach, and Lily of the Valley grove . The public enjoys and accesses the park in a variety of ways: walking, dog-walking, running, cycling, and even horseback riding .

The Pacific Spirit Regional Park's Official Map by Metro Vancouver showing important trails and facilities locations and information.

Management by the Pacific Spirit Park Society

The Pacific Spirit Park Society (PSPS) is a park association officially incorporated in 1998 under the Metro Metro Vancouver Regional Park Partnership program . It is a community of staff and volunteer members who run public education and stewardship programs such as EcoTEAM which removes invasive plants and plants native ones; EcoWATCH which conducts invasive plant mapping and native vs. invasive plant spread monitoring . The society promotes to the public and advises Metro Vancouver parks on the protection, planning and operation of the PSRP. They encourage recreational use while implementing restoration projects in the park .

The Pacific Spirit Park Society EcoTEAM volunteers in action.

Challenges to Existing Management at PSP

Constituting one of the most widespread invasive species in British Columbia, many challenges impact the management of Himalayan Blackberry. It has the ability to grow in a wide variety of locations and is difficult to remove. A high cost is associated with removal, and much time and effort must be spent to ensure no re-growth.

Other issues in tackling the species include identification, collaboration with the public and landowners, and insufficient funding.

Identification

Identifying Himalayan Blackberry can be difficult due to its similarities to other species present in BC. Sometimes misidentified as Rubus ursinus (Trailing Blackberry), a local native species.

Evergreen Blackberry (Rubus laciniatus) is a non-native species closely resembling the Himalayan Blackberry.

Removal Process

Himalayan Blackberry often requires follow-up monitoring to ensure no regrowth following initial removal.

There is a risk to other plants when some control methods, such as mechanical or chemical, are used. Safer options, however, are often more time intensive.

Disturbing seeds in the ground during removal may cause re-growth if not removed.

Cost

The efforts to contain the Himalayan Blackberry have been costly to local and provincial governments, with $350,000 spent in 2016.

In 2021, The BC Provincial Government Spent 12 million dollars on combating invasive species.

Removal processes have a high cost, with some mechanical processes costing $250-$500 per acre. Because of this cost, Government programs like the Invasive Species Council of BC’s “Grow Me Instead” are used to prevent the growth, purchase or trade of the Himalayan Blackberry.  

Public Involvement

Collaboration is considered a foundation for helping combat invasive species in British Columbia by the Invasive Species Council of BC. Collaboration was listed as a challenge in the Invasive Species Strategy for BC.

Public use of the plant for consumption of its berries can lead to the spread of the species.

The BC Government encourages the reporting of invasive species through the Report Invasives app and by email.

Conclusion

Some key takeaways from our research and our own recommendations:

invasive species like Himalayan blackberry are usually introduced and established with a high level of species occurrence due to anthropogenic factors. Governments should enforce policies and communities should conduct monitoring to prevent future invasion.

By evaluating different methods of control, it's most recommended to use manual or chemical control methods in order to deal with Himalayan Blackberry. Different methods can be in tandem in order to produce the most effective, long-term results.

Park societies like PSPS should seek for more funding to steward critical habitats and biodiversity hotspots to prevent excessive public disturbances and restore native species to build ecological resilience against invasive species in the future.

BC policies “future steps sections” corresponding to different challenges & comparable cases on managing invasive blackberry elsewhere in Metro Vancouver - most of BC faces similar challenges when controlling Himalayan Blackberry. Removal, Insufficient funding and cooperation. Increasing sustainable long-term funding and increasing community knowledge are two proposed solutions to the challenges faced on the provincial scale.