Invasive Threaten Species Diversity In Ecosystem Hotspots

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Invasive Threaten Species Diversity In Ecosystem Hotspots

Charles Mkoka Jul 22, 2021 at 12:07 PM UTC views(2179)

LILONGWE, Malawi, July 22, 2021 (AEJ) - Nyika National Park was venue for this year’s World Biodiversity Day held on 22nd May, 2021 under the theme We are part of the solution. One major threat to biodiversity hotspots is the spread of Alien Invasive Species (IAS) now threatening native plant species in key ecosystems in Malawi. CHARLES MKOKA attended the event at Chilinda Camp and asked MPHATSO KALEMBA, Principal Environment Officer and Coordinator of IAS programme in the Department of Environmental Affairs to shade more light on how deadly invasive are in Malawi’s ecosystems.

How would you describe IAS ?

These are plants, animals, microbes which are introduced to new areas or regions, as a result of human activities, where they establish and spread, impacting negatively on biodiversity, agriculture, water resources and human health.

IAS pose one of the most important threats to biodiversity in Malawi. As IAS establish and spread, they outcompete with native species, reducing their abundance and diversity, altering vegetation and reducing ecosystem services.

Kalemba pose in a Pine occupied plantation at Chilinda, Nyika National Park

Can you provide examples and their impacts?

There are a number of IAS that now occupy some biodiversity hotspots in Malawi. The most prominent ones are as follows;

(a) Pine (Pinus Patula) - Pine is a water thirsty plant, pine has the potential to reduce available water for stream flows and water supply downstream which will have negative consequences on the quantity of water available for hydro-electric generation, irrigation and domestic supply. Mulanje Mountain Forest Reserve and Nyika National Park being water catchment areas, the prevalence of this species is a threat to water conservation: - Pine has a negative impact on biodiversity. Pine alters the soil pH and texture making the soil less suitable for other plants and wildlife to flourish in the ecosystem which threatens the abundance of endemic species that are found at the basin. Where pine grows, no other plant grows - Forest fires with pine are more detrimental increasing costs of fire protection and increasing damage caused due to wildfires. In cases of fire, the catchment service of the basin will be threatened and will be prone to soil erosion following fires in heavily invaded areas - Being a biosphere reserve with a potential to be a World heritage site, presence of pine in Mulanje may affect the suitability of this biome for recognition as a heritage site, this has implications on tourism - Reduces abundance of pollinators. Farming communities adjacent to protected areas are dependent on bees and other pollinators for honey making and pollinating flowering plants. Displacement of native flowering plants by Pine also displaces and reduces pollinator population available for honey production - It also reduces abundance of natural enemies of crop pests

(b) Water hyacinth

The hyacinth is an aquatic weed, meaning it colonized water habitats. In Malawi the hyacinth has been a menace to most rivers and it’s widespread in Shire the main outlet of Lake Malawi.

Replaces native biodiversity and reduces abundance of species as it makes the habitat less suitable for other species to grow and flourish. It is that invasive plant that reduces water quantity. In Capetwon, South Africa, the government has spent lots of money trying to remove Black wattle in river streams as one of the solutions to curb water problems. This is one of the worst invasive species.

(d) Himalayan Raspberry (Rubus Ellipticus)

Affects movement of wildlife as it is thorny, reduces abundance of native species

(e) Prosopis

Mostly found in Lower Shire districts of Chikwawa and Nsanje along the road side, and around Lake Chilwa. It has taken up most of the farming and grazing land and displaced the original species.

What impacts and implications are IAS having on ecosystems in Malawi ?

IAS have a great impact on catchment protection and in turn water resources: Most protected areas like Nyika and Mulanje forest reserve are major water catchment areas for hydropower, irrigation and domestic water use. Invasive species like Black wattle, Eucalyptus and Pine can reduce stream flows by 70%.

There are also issues to do with loss of tourism revenue: much of the natural beauty and biodiversity which attracts people to the two protected areas is affected by invasive species. Invasive species affect animal sightings, which is easier in grassland ecosystems than forest ecosystems.

IAS are also major culprits in the reduction of pollinators presence. Farming communities adjacent to the two protected areas are dependent on bees and pollinators for honey making including pollinating flowering plants. Displacement of native flowering plants by IAS also affect and reduces pollinator population available for honey production.

There is also fear of decrease in natural pest control capacity in agricultural systems, pest control problems may be exacerbated by biodiversity loss. Habitat conversion results in reduction or loss of natural enemies of pests

Then comes the economic impact in terms of hydro-electricity by invasive species like water hyacinth (Namasipuni). This result in sedimentation and reduces about 10-12% of power generation. In the long term, this has an impact on hydro power generation and economy as a whole in general.

Which key biodiversity areas are under threat as a result of IAS in Malawi?

Many of the invasive species currently in Nyika National Park were intentionally introduced. In the 1950s the Colonial Development Corporation established a plantation of 542 ha of pines (Pinus patula and P. elliotii), Eucalyptus and Wattle (Acacia mearnsii) at Chilinda, and some smaller plantations elsewhere on the plateau. A number of species introduced as ornamentals around tourist lodges and staff housing have also escaped cultivation such as Desmodium uncinatum and Erigeron karvinskianus. Species such as Tithonia diversifolia, Mimosa diplotricha, Hyptis suaveolens and Lantana camara are abundant in the foothills and pose a potential future threat.

At Mount Mulanje the main invasive species are Mexican pine (Pinus patula), Himalayan raspberry (Rubus ellipticus), Bracken fern (Pteridium aquilinum) and American foxglove (Digitalis purpurea). In addition to these species there are over 50 other invasive plant species such as Lantana camara, Mimosa diplotricha, Acacia mearnsii, Dolichandra unguis-cati, Argemone spp., Tithonia diversifolia, and T. rotundifolia, growing in the foothills within the forest reserve boundary that have the potential to transform habitats and displace native plants.

Proliferation of invasive plants has put many highly vulnerable endemics at great risk of extinction, a situation which is further compounded by the increasing frequency of wildfires and climate change.

IAS research crew captured at Nyika National Park

The Forestry department enlisted the surrounding communities to clear Pinus patula (Mexican pine) and Rubus ellipticus (Himalayan raspberry) out of the mountain.

So far, stories of successful IAS eradication are rare but this is not to rule out they exist. Evident, however, is that while efforts have been taken to eradicate IAS, the incidence of IAS in the country is growing. Malawi’s fifth national report to Convention on Biological Diversity (2014) reports that IAS have increased in number from 29 to 31 with the inclusion of Black wattle and Eucalyptus bug. Other reports put the IAS figures at 45 to 68 (GoM, 2015) and yet other experts estimate that it is well over 100 (Witt, 2021).

The best way forward is to prevent new introduction, prevent further spread and eradicate where possible.

What is being done to contain IAS at Nyika National Park?

Past invasive alien plant management has largely focused on the reduction of the 542 ha pine plantation and only leave behind enough for fuelwood and building materials for use by park staff. However, past attempts at doing so have not been successful as “control measures have not been consistently implemented” and that “staff requires on-site training in control techniques.” Plant species are being lost through the expansion of exotic tree species from Chilinda plantation and seeds of pine are a source of invasion in surrounding grasslands.

What other research interventions are currently underway to contain IAS threat?

There are a number of studies being undertaken under the Global Environment Facility funded IAS project to identify best management practices including use of biological control agents, herbicides, manual and mechanical removal. The best management practices will be adopted on a larger scale. Most of the work focuses in protected area because the problem of invasion is too huge and requires alot of resources to recruit the necessary labour force.

We are therefore asking more organizations to support this effort. In addition, government plans to strengthen surveillance systems, early detection and rapid response to prevent new introduction and establishment of Introduced IAS in our protected areas.

This applies to fisheries as well to prevent invasive fish from being introduced into our water bodies. Risk assessments also need done for any new organism before it is introduced into the environment.

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