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Notes from a presentation at the

Modifying Reproduction in Urban Trees Conference

February 12, 2003 through February 13, 2003

North Carolina Biotechnology Center.

By Kelly Bender

Urban Biologist, Texas Parks and Wildlife, and author, Texas Wildscapes

Contact information for both Ms. Bender and the conference sponsors follows this article

 Currently, land is being converted from agriculture or undeveloped land to suburban sprawl at a rate of 9320 km2/year  (NRCS 2000).  As land becomes more fragmented, these areas become more important to wildlife.

 Green areas within urban development are largely planted with grasses, trees, and ornamental plants from nurseries rather than areas that have been protected from disturbance.  As urbanization and human development increases, those areas’ potential value as wildlife habitat increases.

 So what is habitat, exactly?

It’s simply the place that organisms live and reproduce – and it has to have certain elements to be viable:

Food

Water

And Shelter…

Shelter for wildlife and their young to hide from weather or predators.

 And in an urban area, it is important that the habitat is assembled in a combination that is both usable and accessible to appropriate wildlife.

 Landscapes within urban areas are largely human creations.

 The green places in urban areas are landscaped and managed by humans, and their landscaping and management decisions are based on a number of factors, including aesthetics, values (what they think is important… wildlife? Open places for kids to play? Family time? Bonding with pets? etc.), and intended activity (wildlife watching, soccer games, hiking, picnics, dog walks, etc.).

 Even “undeveloped” lands have generally been invaded by ornamental plants with marginal wildlife value (for plants prized for their flower color or leaf patterns, ornamental horticulture needs rarely include seed, fruit or nectar production) that we use in our landscapes and the pets we keep as companions.

Effects of creating urban habitat (Hunter 2002)

·         More native bird species

·         More ground nesters

·         Fewer introduced bird species

•   More insect-eating birds

·         More over-wintering birds

So, given that urban habitat is very important to the survival of wildlife, and if one of the things we value is wildlife, we need to provide viable wildlife habitat in urban and suburban areas. 

 This doesn’t mean we necessarily have to provide vast acreages of unspoiled wilderness running through the heart of our cities – it simply means we should consider wildlife needs when we are developing and landscaping (really, I’m getting to the biotech considerations… bear with me)

 So let’s take a little closer look at what constitutes good, balanced, and viable habitat…

• Native plants: consider bloom time, fruiting and seeding time – co-adapted with native wildlife
• Increased variety = strength, increase diversity of wildlife it’s able to support
• Think of the community, not just one species.  “Seed A” may not be important to any bird species, but it might be a key host for “Insect A” that forms the basis of “Bird A’s” breeding period diet.
• Layers: many species specialize in particular layers of habitat (Canopy, understory, groundcover)
• Emulating native habitat increases you chance of providing appropriate habitat – plants and structures, and helps create a sense of space.

 Our research shows us that by incorporating these elements into even the most urban of areas will increase the diversity of desirable wildlife.

 With no “Wild Kingdom Wal-Mart” animals are entirely dependant on plants and other animals for their food.  They have co-adapted with plants over thousands of years so that, for example, the hummingbirds migrate at the same time as the flowering seasons in the southern and central US.  And many birds are able to eat the berries that trees produce just at the time that the insect activity is starting to decrease.

 In fact, this co-dependence is so prevalent that wildlife biologists use the term “mutualism” to refer to an interaction between two species that benefits both.  Mutualism is the rule between a great number of plant and animal species: plants provide nourishment while animals aid in plant reproduction.

 Keystone species are those that can be used to assess the overall condition of the resources of a habitat.  These species might be plants, animals, fungi, or anything that is key to the continued health of the ecosystem.  If any of these keystone species is modified in a way that affects its role in the ecosystem, the entire ecosystem will collapse.

 When I was asked to do this talk, one of the things the organizers wanted me to do was address groups of species whose reproductive parts probably would not be important to wildlife.  I immediately thought of wind-pollinated trees… These species produce such copious pollen that can be very unsightly… and can aggravate human allergies.  Since they are wind-pollinated, the flowers aren’t ornate, and they don’t attract pollinators like bees, moths, butterflies, or hummingbirds.  Sounds like a great candidate, right?

 I investigated a little further into different pines, and found that various species of pine are the main food source for the Douglas squirrel, an inhabitant of the western coast from southern British Columbia to northern California.  

Martin, Zim, and Nelson developed a rating system that took into account both the number of species that used a particular plant (survey of 300 vertebrate species) as well as the importance of each plant in that species diet:

 Top 15 Ranked plants

Oak	96
Pine	82
Wild Cherry	81
Dogwood	64
Cedar	75
Maple	61
Hackberry	44
Birch	25
Mesquite	24
Elderberry	79
Serviceberry	58
Sumac	50
Aspen	28
Fir	23
Sagebrush	22

                     

Trees that are particularly important by region:

Understand, however, that trees that are very important in one particular habitat might be washed out in this ranking system to plants that are marginally important in many habitats.

 

Northeast Region

·        Oak

·        Wild Cherry

·        Pine

·        Dogwood

·        Maple

·        Beech

·        Blueberry

·        Birch

·        Sumac

·        Aspen

 

Southeast Region

·        Oak

·        Pine

·        Wild Cherry

·        Blueberry

·        Hickory

·        Black gum

·        Holly

·        Beech

·        Maple

·        Persimmon

 

Prairie Region

·        Oak

·        Hackberry

·        Wild Cherry

·        Cedar

·        Sagebrush

·        Snowberry

·        Sumac

·        Persimmon

·        Mulberry

·        Dogwood

 

Mountain-Desert Region

·        Pine

·        Sagebrush

·        Mesquite

·        Oak

·        Cedar

·        Manzanita

·        Douglas Fir

·        Wild Cherry

·        Serviceberry

·        Gooseberry

 

Pacific Region

• Pine

• Oak

• Elderberry

•  Manzanita

• Buckthorn

• Wild Cherry

• Ceanothus

• Cedar

• Douglas Fir

• Dogwood

So, when considering a tree or shrub for a candidate for creating a sterile plant, please consider this:

 Red light
-Do not proceed-

l   Native plants

 Amber light
-Proceed with caution-

l  Non-native, introduced species

            –But watch out – Is it related to a native species?

            –Overuse of a sterile plant can result in reduced native plants?

 

Green light
 -Proceed with abandon-

l  NOTHING!