A 20-year fight against the Blackwood Acacia (Acacia melanoxylon)

The Acacia is an invasive plant species introduced in Galicia between the 50s and 60s during the final period of Franco's regime and began to reproduce with remarkable success throughout the 70s because of the forest fires in the Galician mountains. In Vigo, the most widespread is the Acacia Melanoxylon or Blackwood Acacia.

This invasive species begins to be a serious problem for the Galician mountains, as or more serious than the eucalyptus, due to its rapid and uncontrolled growth and, above all, its virulent characteristics when a fire occurs. This is something that the inhabitants of Vigo and neighboring villages were able to witness after the fateful wave of fires in October 2017.

Like the eucalyptus, this Acacia’s wood is of very low quality and is therefore not suitable for the manufacture of furniture. Its proliferation replaces the native Galician forest formed by oaks, alders and birch trees, among others, and transforms the forests into high-risk places in case of fire. 

For this reason, and to try to eradicate a potential danger, an initiative was carried out against the uncontrolled population of Acacias in the A Madroa mountain on June 7, 2019. The activity was organized by the Neighbour Woodlands Community of Teis and the Arlequin group.

It was attended by UVigo researchers and about fifteen volunteers who carried out an experimental project. The initiative is part of a series of sessions related to eucalyptus removal organized in Galicia and will culminate at A Guía mountain on June 15, 2019.

 A deep struggle

Manuel López, member of the Teis Common Woodlands Community, explains that the fight against the Acacia is profound: "We have been working on this issue for 21 years and I can only describe it as a war. It can take eight years from the time we start with an area until we completely repopulate it". The biggest problem with Acacias is the ease with which they grow back. "If you don't have enough resources to do the job right, it's better not to start because if you cut one Acacia, the next day three more will grow in its place."

The Galician climate is very favorable for the reproduction of the Acacia because it needs water and sunlight to develop. Lopez points out that something essential to combat the Acacia is to remove some of these factors. "The key is for the Acacia to have enough shade, through the overplanting of native plant species that create a dense vegetative cover, which is technically known as canopy.” The coordinator of the activity, Xulian Martínez, explains that the two ways to prevent the Acacia from growing back are "pulling them out by the roots or peeling the tree stumps to dry them out". To remove them whole, it was necessary to put a little bit of imagination and the community members themselves devised a clamp that can be attached to a tractor and that allows them to remove the whole tree in one piece.

In this case, it is relevant because the Acacia roots are extremely deep, "something that does not occur with other invasive species such as eucalyptus," explains López.

EXPERIMENT

Jonathan Rodríguez, from the Faculty of Biology at UVigo, is responsible for the experiment conducted at the A Madroa mountain with Professor Luis González, which aims to study the effectiveness of different methods in a comparative way. To do this, the area was divided into plots with an Acacia stump inside each one. Some trees had their bark cut off, others had herbicides applied to the stump and the last group was given "a saturated saline solution that, if it works, would be a non-contaminating solution - at least for humans - and very accessible to anyone who works the land." 

He explains that this last element is important because "there are no previous studies in which this type of procedure has been used". In addition, "it is humanly impossible to eliminate all the seeds from the soil, so the remaining objective is to control regrowth". The project does not yet have funding of any kind, but Rodríguez hopes to obtain it after this test "and to repeat the experiment in other nearby woodland communities."

AT THE MOMENT OF TRUTH NO ONE HELPS US

According to López, the government's role is very deficient: "A lot of political will and continued investment is needed to actively support reforestation. We see some propaganda in the way politicians express themselves in the media, but at the moment of truth, nobody helps us here”. As for Martinez, he complains that there is aid for burned areas, "but not for those of us who work to prevent fires."

The commoner with more than twenty years of experience behind him is very clear: "Of course there are arsonists, but the ultimate responsible for the fires is the Administration for allowing the forests to be in this condition. There is a lot of talk about clearing forests to prevent fires, but I do not hear of it being done in other places like France, because a native forest does not need it."

He also believes that the current fire law "establishes parameters that cannot be met" and that this is a complex issue because "there are many economic interests in the sector so that the cards do not move." He also criticizes that in recent years the forest is being repopulated, without a previous environmental study, with paulownia, another foreign species "of even faster growth than the acacia" used for biomass. "In a few years we may be talking about a situation similar to what we are experiencing with other species," he stresses.

THE COLLECTIVE AS A DRIVING FORCE

Among the people who carried out the work were members of Arlequín, a group of young people under thirty years old who live in the surroundings of mount A Guía. They decided to join together to collaborate in favor of a healthy forest. One of its members, Iris Docampo, considers that it was "fundamental" to make the decision to join because "more things have been done in the few months we have been working together than in the five years I have been trying to do things on my own."

Unlike A Madroa, in A Guía "there are few large acacias because they are younger", so the community can fight it without having to use heavy machinery "to which it does not have access". In theory, the City Council is in charge of cleaning the forest but in practice this is not the case. "It only cleans the visible areas of the walking areas and parks, but the real forest areas are totally neglected," she complains. Docampo warns of the danger that a fire would have in A Guía right now: "it would leave the oak grove and little else."