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FREQUENTLY ASKED QUESTIONS ABOUT INVASIVE ALIEN SPECIES

1. How should I deal with invasive alien species that are used by animals for food or shelter?

2. Won’t biological control agents attack native species?

3. Doesn’t erosion after the removal of invasive alien plants make the problem worse?

4. Can we really afford to spend large sums of money on clearing alien plants?

5. Are the herbicides used in alien plant control environmentally friendly?

6. Isn´t the use of herbicides in the control of invasive alien species dangerous for animals, especially for amphibians?

7. What kinds of species are regarded as a threat?

8. Is forestry the main culprit in spreading invading alien plants?

9. Are we sure we are doing the right thing by clearing large areas?

10. Should we clear plants that provide some form of benefit?

11. How can I help?

1. How should I deal with invasive alien species that are used by animals for food or shelter?
Groups of invasive alien plants can in some cases provide habitat for birds or other animals. Examples include birds that nest on large trees and animals that feed on their fruit. The problem is that there are many more species that are displaced by invasive alien species than benefited by them. Many of the native species that are displaced are rare or endemic, while often those which find shelter or food in invasive alien species are not natives themselves or are not priorities for conservation.

Long-term studies tend to show that the removal of invasive alien plants that provide food or shelter for animals generates benefits in biodiversity, as it allows the environment to get back to its natural balance of populations. Dominance by invasive species is always a problem, as invasives favor few species and displace the majority of them as their populations grow. Most of the native species cannot find benefits in growing invasions.

2. Won’t biological control agents attack native species?
No. Before biocontrol agents are considered for release, they are subject to a period in quarantine. During this time, they are carefully screened to ensure that they will attack only the target alien plant species, and that they can complete their life cycles and reproduce only on the target plant species. Any biocontrol agent that is in any way capable of damaging indigenous plants or important crops will not be released.

3. Doesn’t erosion after the removal of invasive alien plants make the problem worse?
There is always concern that control practices may cause erosion if the areas cleared are not properly restored. This concern is important, so soil conservation and restoration practices are part of invasive alien species control. It is also true, however, that fires generated by fire-prone invasive alien species tend to result in serious erosion. In one way or the other, if invasive alien plants are retained they cause gradually more impact and are more difficult and more expensive to remove in the long term. For this reason, not removing alien plants weighs more negatively than erosion processes, as these can be more easily controlled and managed as part of the clearing operations.

4. Can we really afford to spend large sums of money on clearing alien plants?
All of the economic studies done to date indicate that clearing operations are cost effective in terms of water savings. In most studies, this conclusion has been reached without even considering the additional benefits for catchment stability, biodiversity, and job creation. Studies also show that clearing as soon as possible is far more efficient in economic terms than leaving the problem to be dealt with later. Given the significant impacts predicted, the question would be better phrased in terms of whether we can afford not to clear!

5. Are the herbicides used in alien plant control environmentally friendly?
No. The solution for this problem lies in the localized use of the herbicide without contamination of the natural environment the species is invading. Wider spread applications are only adequate in areas that are completely dominated by invasive alien species. Still, the impacts and persistence of the herbicide are infinitely smaller and less serious than retaining invasive alien species on a site. There is a level of tolerance for impacts upon control actions, and this needs to be evaluated in each situation.

Only legally registered herbicides are used in control practices. Before being registered, some of these products undergo strict environmental and human health assessments. Technology also works in favor of better herbicides that degrade rapidly and are less toxic to non-target species. Many of these products are manufactured in developed countries where the standards of environmental care are very high. Some herbicides degrade in 30-45 days, and do not affect animal physiology.

Those who have the opportunity to participate in control work using herbicides easily understand how essential they are for the success of the work and how side impacts can be mitigated. Herbicides are most often applied directly on cut stumps of trees to avoid resprouting, which degrade far slower than the product itself.

Restrictions to the use of chemical products often prevent proper control work in the field and may lead to the loss of important natural áreas and of biodiversity. Read more

6. Isn´t the use of herbicides in the control of invasive alien species dangerous for animals, especially for amphibians?
The use of herbicides in the control of invasive alien species is different from the traditional agricultural use:

a) large volumes of herbicide are often used in agriculture while for environmental use low volume applications are the norm.

b) herbicide applications are extremely punctual. One of the most common treatment methods is to apply herbicide directly on cut stumps. It is perfectly possible to avoid side effects.

c) applications are made using a colourful dye, which helps the operator and his supervisors to clearly see signs of any spill or inadequate use, improves the precision of applications and reduces the volume used, as operators will not redo treatments unnecessarily because they can easily see the treated areas.

d) in case of control of grasses, there are two possibilities for application avoiding impacts: the first refers to preparing the area by mowing the grasses first, and then applying herbicides only to the stumps when the grasses sprout back; the second is to use a chemical rod and apply herbicides that kill plants through direct contact at a certain level from the soil, so they do not reach the ground.

The control of invasive alien species is very often meant to restore natural ecosystems, and many sound methods of chemical control have been developed to avoid negative impacts.


7. What kinds of species are regarded as a threat?
All biological groups contain species with potential for invasion. In some countries, such as South Africa, there is much focus on trees due to the depletion of water resources. The same risk exists in Brazil from intensive conversion of grasslands and savannas into forest plantations using non-native species.

In Brazil, we already know that invasive alien species are present in all terrestrial, freshwater and marine ecosystems. Prevention measures to avoid the introduction of more species are necessary to avoid future impacts, and control measures are crucial to mitigate existing impacts.

Certain plants can alter ecosystem functioning and are therefore called “transformers”. These species cause great concern and are usually priorities for control, eradication and regulations when under economic use.

The common characteristics of invasive alien species, regardless of the type of organism, are their prolific reproduction rates, flexibility of adapting to different environmental conditions and the capacity to dominate new areas and displace native species.

8. Is forestry the main culprit in spreading invading alien plants?
No. Forest plantations contribute with part of the tree invasions and will be reduced as forest companies incorporate proper management practices to avoid spread of the species they use, as required by certification. In the Paraná state grasslands, in the South of Brazil, the main source of seeds for the widespread pine invasions are pine trees planted along the highways in the 1950s and 60s. Roads are pathways that facilitate invasion, and as such also require proper management practices to mitigate environmental impacts.

Forest plantations using invasive alien species for pulp, paper or timber, couple with the conversion of natural ecosystems, are surely a concern and need to be properly managed in the aspects of spread and also in water use by fast-growing species, especially in grassland and savanna ecosystems.

9. Are we sure we are doing the right thing by clearing large areas?
Yes. A responsible approach to environmental management demands that we act on the best available information. Indications are that the impacts of invading alien plants are significant enough to warrant large-scale clearing operations, even if their success is not always guaranteed. We cannot afford to wait until effective rehabilitation methods are developed before we deal with all situations as the impacts grow daily as alien plants spread, and the problem will soon reach unaffordable, as well as irreversible, proportions.

10. Should we clear plants that provide some form of benefit?
This is an important question and has a variable response. There are always arguments to keep species which generate benefits such as firewood, food or income generation. However, these benefits need to be critically compared to the costs these species generate when they become invasive. This cost analysis must include ecosystem services, damage to other rural properties and costs of control required. If these costs are higher than the benefits, then there is a reason to remove the plants.

On the other hand, if it is possible to cultivate or breed an invasive alien species in confined management, without harming other native species or the environment, and the control of the species spread is viable, it can be used.This level of control is easier to attain for plants whose seeds are wind dispersed or that reproduce vegetatively. Animal breeding controlling escapes is nearly impossible, as many invasion problems can show. Common examples are tilapia, carp, catfishes and trouts, the giant African snail and the bull frog. These species damage natural ecosystems and the native fauna, are very difficult to control and nearlyl impossible to eradicate, which implies in ongoing control costs that will undoubtedly, in the long term, represent larger sums that the benefits they might have provided.

A crucial issue in this assessment is to clarify who benefits and who pays the costs if there is a problem. Benefits are usually placed in the hands of small groups of economic interest that do not usually take up the responsibility of caring for proper management and control, while the damage and the costs implied in control and restoration tend to be taken up by governments and shared by society. It is also common that large investors retain the benefits while small farmers lose production and take up control costs or loss of water resources. This analysis requires a balanced vision that is fair for all in the equitative benefit sharing of biodiversity resources.

11. How can I help?
If you are a land owner, you should take responsibility for the problem on your own land. Establish which invading alien plants occur on your land and the options you have to bring them under control. Clear invasive species and do not cultivate species you cannot properly care for. Plants that are dispersed by animals cannot be controlled and must not be used.

Learn about invasive alien plants that you might be cultivating in your own garden. Use more native plants as they bring benefits to native animals and are part of a balanced ecosystem.

If you own pets, never release them in natural areas. Even cats and dogs are voracious predators and need to be contained and well fed to reduce their hunting instincts. Control the proliferation of your pets and never abandon them to take care of themselves.

You can help generate more public awareness on biological invasions. You can also visit protected areas that maintain voluntary work for clearing invasives.

Contribute with data to national databases on invasive alien species. If you have information for Brazil, go to National survey on alien invasive species.
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