1998-1999 weed survey summary statistics
The 1998 survey began with approximately 40 questions, mostly relating to
contact information, etc. This was followed by questions
questions specific to the invasive species
reported
(see footnote 1).
For each weed taxon, approximately 50 questions
were used to gather information on the nature of the infestation,
the threats it posed,
the methods being used to manage the weed, and the success of those methods.
It is important to be cautious when interpreting the data obtained in this survey. Three caveats are given below:
1)Area incompleteness: The total area managed by respondents of this survey was about 854,000 hectares (2.1 million acres). While this area was distributed among all 50 states of the USA, the vast majority of distributed among all 50 states of the USA, the vast majority of the USA's wild lands are not included in the survey. (For comparison, Yellowstone National Park alone covers 890,000 hectares.) This sampling bias can be considerable---for example no marine habitats were spanned by the survey results. As such, this survey should not be considered to be a complete sampling of invasive species across the USA.
2)Inconsistencies in staff expertise or interest: The emphasis placed upon invasive species management is not the same at all TNC sites; similarly, staff training on invasive species issues is not uniform. We have observed that programs or staff that are more familiar with invasive species issues tend to report a greater number of invasive species. Thus, the numbers of invasive species reported (and the degrees of invasion) are often a reflection of the extent of invasive species invasions as well as staff expertise.
3)Heterogeneity of management goals: Even if a taxon is a well known invasive weed, staff are less likely to report it if it does not interfere with their management goals for a site.
It is important to be cautious when interpreting the data obtained in this survey. Three caveats are given below:
1)Area incompleteness: The total area managed by respondents of this survey was about 854,000 hectares (2.1 million acres). While this area was distributed among all 50 states of the USA, the vast majority of distributed among all 50 states of the USA, the vast majority of the USA's wild lands are not included in the survey. (For comparison, Yellowstone National Park alone covers 890,000 hectares.) This sampling bias can be considerable---for example no marine habitats were spanned by the survey results. As such, this survey should not be considered to be a complete sampling of invasive species across the USA.
2)Inconsistencies in staff expertise or interest: The emphasis placed upon invasive species management is not the same at all TNC sites; similarly, staff training on invasive species issues is not uniform. We have observed that programs or staff that are more familiar with invasive species issues tend to report a greater number of invasive species. Thus, the numbers of invasive species reported (and the degrees of invasion) are often a reflection of the extent of invasive species invasions as well as staff expertise.
3)Heterogeneity of management goals: Even if a taxon is a well known invasive weed, staff are less likely to report it if it does not interfere with their management goals for a site.
Who responded/Areal coverage
110 respondents
All 50 USA states
920 preserves represented
854,000 hectares(2,110,000 acres)
Levels of concern: % of managers who said... 49%: "weeds are one of my top 2 or 3 concerns"
84%: "weeds are one of my top 10 concerns"
5%: "weeds are not a problem"
Threats from weeds 1400+ native communities are threatened
900+ native species are threatened
Most frequently reported weeds (10 or more reports) Lonicera japonica; 24 reports, 1190 weed-hectares
Phragmites australis; 23 reports, 697 weed-hectares
Lythrum salicaria; 22 reports, 392 weed-hectares
Alliaria petiolata; 19 reports, 523 weed-hectares
Cirsium arvense; 19 reports, 539 weed-hectares
Euphorbia esula; 15 reports, 545 weed-hectares
Melilotus officinalis/M. alba; 15 reports, 1440 weed-hectares
Bromus spp. (see footnote 2); 17 reports, 53,500 weed-hectares
Tamarix spp. (see footnote 3); 14 reports, 2480 weed-hectares
Lonicera maackii; 13 reports, 423 weed-hectares
Rosa multiflora; 12 reports, 57 weed-hectares
Phalaris arundinacea; 12 reports, 369 weed-hectares
Centaurea biebersteinii; 11 reports, 396 weed-hectares
Ailanthus altissima; 11 reports, 98 weed-hectares
Frangula alnus; 10 reports, 606 weed-hectares
TNC control efforts 292 herbicide programs
260 cutting/mowing programs
245 pulling programs
210 burning programs
116 cultural/other programs
19 biocontrol programs
Overall, 1142 weed management programs in 1998
Overall, 36,000 staff-hours in 1998
Overall, 30,000 volunteer-hours in 1998
Area occupied by all weeds & largest infestations reported (see footnote 4) 190,000 invaded weed-hectares (480,000 weed-acres)
890,000 uninvaded weed-hectares (2,200,000 weed-acres) are ripe for invasion
"Bromus species" (see footnote 5): 24,900 weed-hectares (61400 weed-acres)
"Hordeum species" (see footnote 6): 24,300 weed-hectares (60000 weed-acres)
Bromus madritensis subsp. rubens: 24,300 weed-hectares (60000 weed-acres)
Lolium multiflorum & L. perenne: 24,300 weed-hectares (60000 weed-acres)
Avena barbata & A. fatua: 24,300 weed-hectares (60000 weed-acres)
Centaurea solstitialis: 7440 weed-hectares (18370 weed-acres)
Juniperus virginiana (see footnote 7): 6820 weed-hectares (16850 weed-acres)
Taeniatherum caput-medusae: 4600 weed-hectares (11360 weed-acres)
Managers' estimations of likelihood of success 28%: "the probability of controlling my weeds is high"
34%: "the probability of controlling my weeds is medium"
24%: "the probability of controlling my weeds is low"
14%: did not respond
Nonplant invaders 71% of respondents noted invasions or population problems with organisms other than plants
65 types of animals were reported
#1 Most frequently cited: deer, 26 reports
#2 Most frequently cited: exotic fish, 18 reports
#3 Most frequently cited: pigs, 17 reports
#4 Most frequently cited: feral/stray dogs & cats, 17 reports
Other interesting facts A total of 271 weed taxa were reported
169 weed taxa were reported once once.
All 50 USA states
920 preserves represented
854,000 hectares(2,110,000 acres)
Levels of concern: % of managers who said... 49%: "weeds are one of my top 2 or 3 concerns"
84%: "weeds are one of my top 10 concerns"
5%: "weeds are not a problem"
Threats from weeds 1400+ native communities are threatened
900+ native species are threatened
Most frequently reported weeds (10 or more reports) Lonicera japonica; 24 reports, 1190 weed-hectares
Phragmites australis; 23 reports, 697 weed-hectares
Lythrum salicaria; 22 reports, 392 weed-hectares
Alliaria petiolata; 19 reports, 523 weed-hectares
Cirsium arvense; 19 reports, 539 weed-hectares
Euphorbia esula; 15 reports, 545 weed-hectares
Melilotus officinalis/M. alba; 15 reports, 1440 weed-hectares
Bromus spp. (see footnote 2); 17 reports, 53,500 weed-hectares
Tamarix spp. (see footnote 3); 14 reports, 2480 weed-hectares
Lonicera maackii; 13 reports, 423 weed-hectares
Rosa multiflora; 12 reports, 57 weed-hectares
Phalaris arundinacea; 12 reports, 369 weed-hectares
Centaurea biebersteinii; 11 reports, 396 weed-hectares
Ailanthus altissima; 11 reports, 98 weed-hectares
Frangula alnus; 10 reports, 606 weed-hectares
TNC control efforts 292 herbicide programs
260 cutting/mowing programs
245 pulling programs
210 burning programs
116 cultural/other programs
19 biocontrol programs
Overall, 1142 weed management programs in 1998
Overall, 36,000 staff-hours in 1998
Overall, 30,000 volunteer-hours in 1998
Area occupied by all weeds & largest infestations reported (see footnote 4) 190,000 invaded weed-hectares (480,000 weed-acres)
890,000 uninvaded weed-hectares (2,200,000 weed-acres) are ripe for invasion
"Bromus species" (see footnote 5): 24,900 weed-hectares (61400 weed-acres)
"Hordeum species" (see footnote 6): 24,300 weed-hectares (60000 weed-acres)
Bromus madritensis subsp. rubens: 24,300 weed-hectares (60000 weed-acres)
Lolium multiflorum & L. perenne: 24,300 weed-hectares (60000 weed-acres)
Avena barbata & A. fatua: 24,300 weed-hectares (60000 weed-acres)
Centaurea solstitialis: 7440 weed-hectares (18370 weed-acres)
Juniperus virginiana (see footnote 7): 6820 weed-hectares (16850 weed-acres)
Taeniatherum caput-medusae: 4600 weed-hectares (11360 weed-acres)
Managers' estimations of likelihood of success 28%: "the probability of controlling my weeds is high"
34%: "the probability of controlling my weeds is medium"
24%: "the probability of controlling my weeds is low"
14%: did not respond
Nonplant invaders 71% of respondents noted invasions or population problems with organisms other than plants
65 types of animals were reported
#1 Most frequently cited: deer, 26 reports
#2 Most frequently cited: exotic fish, 18 reports
#3 Most frequently cited: pigs, 17 reports
#4 Most frequently cited: feral/stray dogs & cats, 17 reports
Other interesting facts A total of 271 weed taxa were reported
169 weed taxa were reported once once.
Footnotes
#1: We let the respondent determine which species were invasive weeds for their sites. However, we provided some guidance at the beginning of the survey: "Weeds are any plants that interfere with your management goals. They are usually non-native species that spread, or at least persist, on the site. Japanese honeysuckle (Lonicera japonica), leafy spurge (Euphorbia esula), and water hyacinth (Eichhornia crassipes) are weeds commonly found in in North American or Hawaiian natural areas. Occasionally, native species move into and change the character of preserve habitats-these plants are also considered weeds. For example, eastern red cedar (Juniperus virginiana) is a weed in some areas of its native range where fire suppression has allowed it to invade prairies."
#2: This guild includes Bromus inermis, B. rubens, B. sterilis, B. tectorum, and unidentified Bromus spp.
#3: This guild includes Tamarix chinensis, T. ramosissima, and unidentified Tamarix spp.
#4: The unit "weed-acre" is defined for a site as being the sum of all the acreages of the various, possibly overlapping weed infestations on a site. For example, a ten acre preserve completely invaded by four weeds would contribute 40 weed-acres. Because sites often have more than one troublesome weed, the weed-acres/weed-hectares reported in the survey are greater than the values for the total area of the survey.
#5: This includes unidentified/unspecified bromes, and includes Bromus catharticus, B. diandrus, B.hordeaceus, B. inermis, B. madritensis subsp. rubens, B. tectorum, and perhaps others.
#6: This includes unidentified/unspecified species, and includes Hordeum marinum, H. murinum, and perhaps others.
#7: This species is native to the USA but can be invasive within its range if natural fire regimes are suppressed.
#1: We let the respondent determine which species were invasive weeds for their sites. However, we provided some guidance at the beginning of the survey: "Weeds are any plants that interfere with your management goals. They are usually non-native species that spread, or at least persist, on the site. Japanese honeysuckle (Lonicera japonica), leafy spurge (Euphorbia esula), and water hyacinth (Eichhornia crassipes) are weeds commonly found in in North American or Hawaiian natural areas. Occasionally, native species move into and change the character of preserve habitats-these plants are also considered weeds. For example, eastern red cedar (Juniperus virginiana) is a weed in some areas of its native range where fire suppression has allowed it to invade prairies."
#2: This guild includes Bromus inermis, B. rubens, B. sterilis, B. tectorum, and unidentified Bromus spp.
#3: This guild includes Tamarix chinensis, T. ramosissima, and unidentified Tamarix spp.
#4: The unit "weed-acre" is defined for a site as being the sum of all the acreages of the various, possibly overlapping weed infestations on a site. For example, a ten acre preserve completely invaded by four weeds would contribute 40 weed-acres. Because sites often have more than one troublesome weed, the weed-acres/weed-hectares reported in the survey are greater than the values for the total area of the survey.
#5: This includes unidentified/unspecified bromes, and includes Bromus catharticus, B. diandrus, B.hordeaceus, B. inermis, B. madritensis subsp. rubens, B. tectorum, and perhaps others.
#6: This includes unidentified/unspecified species, and includes Hordeum marinum, H. murinum, and perhaps others.
#7: This species is native to the USA but can be invasive within its range if natural fire regimes are suppressed.