The perception of Spanish land managers of invasive alien plants
A questionnaire was sent to land managers in Spain in order to evaluate their perception regarding plant invasions, and to gather information about management activities on invasive alien plants. Respondents were senior managers from all public environmental administrations with responsibility for biodiversity conservation of natural areas at both national and local level. The environmental sectors assessed included forestry, water management, nature conservation, coastal protection, and urban green spaces departments, but the agricultural sector was not surveyed. Seventy (70) questionnaires were received.
Results highlighted that environmental managers in Spain were clearly aware of the risks posed by biological invasions, and ranked them as an intermediate threat to biodiversity, after landscape changes such as habitat loss, urbanization, habitat fragmentation and land use change. In total, 193 alien plants were identified as noxious, and 109 were subject to management measures.
The taxa most frequently identified as noxious were Carpobrotus spp., Eucalyptus spp., Ailanthus altissima, Robinia pseudoacacia, Acacia spp. and Cortaderia selloana. About 94% of noxious species were found in at least one protected area. Regarding the magnitude of the impacts caused by noxious species, 35% of the cases were perceived as having a high impact on natural areas, and 28.5% a low impact. The main ecological impacts reported were competition with native species for space and soil resources, species loss and changes in the integrity and stability of ecosystems. Other impacts included indirect effects on the fauna due to changes in their behaviour or modification of the habitat, changes in the composition and structure of riparian forests, soil erosion and degradation, etc. Respondents also provided names of native species negatively affected by aliens:
- In Cap de Creus (Natural Park in Cataluña), Carpobrotus spp. outcompetes Limonium gerondense (Plumbaginaceae), Armeria ruscinonensis (Plumbaginaceae), Astragalus massiliensis (Fabaceae) and Seseli farrenyi (Apiaceae);
- In Isla Grossa (Murcia), Carpobrotus spp., Acacia spp. and Agave americana are thought to compete with Lycium intricatum (Solanaceae), Salsola spp. (Chenopodiaceae) and Withania frutescens (Solanaceae);
- In the Miña River, the presence of Azolla spp. leads to a loss in the cover of Magnopotamion and Parvopotamion vegetation type;
- On Fuerteventura (Islas Canarias), Pennisetum setaceum outcompetes Launaea arborescens (Asteraceae), Euphorbia balsamica and E. regis jubae (Euphorbiaceae), Suaeda spp. and Salsola spp. (Chenopodiaceae).
Eighty eight percent (88%) of the invasive plants considered to have a high impact were being managed, while the remaining cases (12%) were not being managed because control was not feasible (species too widely distributed), or affordable. In addition, 78% of species with low impact were managed, often as part of a wider programme targeting high impact species. Management activities were prioritized in the following order: direct control, prevention, education and outreach, and legislation was perceived as the least relevant and efficient measure. The main goal of management appeared to be containment (41%) or complete eradication of the invasive species (37%). Prevention through legislation or education of the general public was only used in 22% of the cases. In most cases, mechanical methods (71%) have been used as they are considered less harmful to the environment, in 25% of the cases mechanical methods were combined with herbicides (usually glyphosate). Only 3% of the cases applied solely herbicides. In 85% of the cases, control measures were followed by annual monitoring to detect reinfestation, but there were only a few cases of this monitoring beign undertaken with long term goals. Restoration of habitats was undertaken in 29% of the cases. Estimates of costs were provided for 41% of the cases, mostly related to direct management activities. Total expenditure was calculated as around 50 million euros over the last decade for all species concerned. Ninety five percent of this total expenditure was targeted on only 5 species as shown in the table below. These costs are considered to be largely underestimated.
The species which are considered to be the most invasive according to land managers in Spain are listed below, together with their management costs. This table also indicates the numbers of Autonomous Communities (AC) where species are reported as noxious and where they are managed (Spain being divided in 19 AC).
|
Species
|
N° of AC where present
|
N° of AC where managed
|
Costs in €
|
|
Acacia spp. (Fabaceae)
|
12
|
7
|
90,000
|
|
Agave americana (Agavaceae)
|
12
|
3
|
57,000
|
|
Ailanthus altissima (Simaroubaceae) EPPO List of Invasive Alien Plants
|
12
|
6
|
28,675
|
|
Aloe spp. (Liliaceae)
|
4
|
1
|
|
|
Amaranthus spp. (Amaranthaceae)
|
17
|
0
|
|
|
Arctotheca calendula (Asteraceae)
|
10
|
3
|
15,000
|
|
Arundo donax (Poaceae)
|
15
|
1
|
|
|
Aster squamatus (Asteraceae)
|
16
|
0
|
|
|
Araujia sericifera (Asclepiadaceae) EPPO Alert List
|
8
|
0
|
|
|
Artemisia spp. (Asterceae)
|
13
|
0
|
|
|
Azolla filiculoides (Azolaceae) EPPO List of IAS
|
8
|
2
|
1,000,000
|
|
Baccharis halimifolia (Asteraceae) EPPO List of IAS
|
3
|
3
|
|
|
Buddleia davidii (Buddlejaceae) EPPO List of IAS
|
7
|
2
|
|
|
Carpobrotus spp. (Aizoaceae) EPPO List of IAS
|
10
|
8
|
2,886,683
|
|
Conyza spp. (Asteraceae)
|
17
|
0
|
|
|
Cortaderia selloana (Poaceae) EPPO List of IAS
|
11
|
7
|
8,600
|
|
Datura stramonium (Solanaceae)
|
16
|
2
|
|
|
Disphyma crassifolium (Aizoaceae)
|
4
|
0
|
|
|
Egeria densa (Hydrocharitaceae) EPPO List of IAS
|
2
|
1
|
|
|
Eichhornia crassipes (Pontederiaceae) EPPO A2 List
|
3
|
3
|
6,700,000
|
|
Eucalyptus spp. (Myrtaceae)
|
13
|
8
|
31,528,594
|
|
Fallopia japonica (Polygonaceae) EPPO List of IAS
|
6
|
2
|
|
|
Ipomoeae spp. (Convolvulaceae)
|
14
|
3
|
|
|
Kalanchoe spp. (Crassulaceae)
|
-
|
1
|
|
|
Lantana spp. (Verbenaceae)
|
5
|
0
|
|
|
Ludwigia spp. (Onagraceae) EPPO List of IAS
|
2
|
2
|
|
|
Nicotiana glauca (Solanaceae)
|
8
|
2
|
|
|
Oenothera biennis (Onagraceae)
|
14
|
2
|
|
|
Oenothera drummondii (Onagraceae)
|
2
|
1
|
|
|
Oenothera glazioviana (Onagraceae)
|
14
|
3
|
|
|
Opuntia spp. (Cactaceae)
|
13
|
4
|
4,000
|
|
Oxalis pes-caprae (Oxalidaceae) EPPO List of IAS
|
11
|
2
|
|
|
Paspalum spp. (Poaceae)
|
17
|
0
|
|
|
Pennisetum setaceum (Poaceae) EPPO Alert List
|
3
|
1
|
6,203,300
|
|
Pittosporum tobira (Pittosporaceae)
|
1
|
1
|
6,000
|
|
Platanus hybrida (Platanaceae)
|
8
|
2
|
|
|
Ricinus communis (Euphorbiaceae)
|
8
|
1
|
|
|
Robinia pseudoacacia (Fabaceae)
|
17
|
3
|
|
|
Senecio spp. (Asteraceae) EPPO List of IAS
|
11
|
3
|
19,600
|
|
Solanum bonariense (Solanaceae)
|
9
|
0
|
|
|
Sorghum halepense (Poaceae)
|
15
|
0
|
|
|
Spartina patens (Poaceae)
|
9
|
0
|
|
|
Tradescantia fluminensis (Commelinaceae)
|
8
|
3
|
|
|
Tropaeolum majus (Tropaeolaceae)
|
10
|
1
|
|
|
Xanthium spinosum (Asteraceae)
|
16
|
0
|
|
|
Xanthium strumarium (Asteraceae)
|
13
|
2
|
|
Other species, although not recorded as the most invasive according to the results of the survey, were associated with management costs:
- Rumex lunaria (Polygonaceae): 86,000 €
- Ageratina adenophora (Asteraceae): 23,109 €
- Plectranthus australis: 6,251 €
- Fallopia aubertii (Polygonaceae): 6,00 €
- Hakea sericea (Proteaceae) (EPPO Alert List): 2,000 €
- Panicum repens (Poaceae): 1,000 €
- Myoporum spp. (Myoporaceae): 400 €
- Lonicera japonica (Caprifoliaceae): 200 €
Sources
Andreu J, Vilá M, Hulme PE (2009) An assessment of stakeholder perceptions and management of noxious alien plants in Spain. Environmental Management 43, 1244-1255.