data jungle adventures

Desert environments seem to lack life and appear hostile to any organism. While we might consider deserts to be vast spaces of arid land, life in the ecosystem is plentiful, very specialised and rather diverse and fragile. On the surface, invasive species might seem relatively harmless in an environment where little native biodiversity exists. Plants, for example, will thrive when the conditions are perfect (after rain or at lower temperatures), and when the conditions are too stressful, they store resources.

While introducing hardy generalists to hyper-arid environments may seem to provide more benefits than threats, invasive plants quickly become an environmental threat in deserts worldwide.

Competition in the void: from invisible biodiversity to single species communities

Alien or invasive plants compete with native plants. This changes wildlife habitats, resource availability, and diversity of seedbanks and can also cause problems with the spread of fire, especially in areas where fires are infrequent.

Invasive species alter ecosystems and their composition by outcompeting natives over resources such as water, light (also relatively abundant in our context), nutrients or resistance against predators or other antagonists. This ultimately leads to landscapes that are dominated by few species. For example, deserts blend plant communities vary across seasons; they change into a landscape dominated by few species.

Aliens and non-native are defined as introduced to a novel location in general. After their establishment, often nurtured in gardens or indirectly in agricultural settings, they become naturalised and form poluations and offspring without human support. Aliens are only called invasive if they have a negative impact on the native ecosystem. What is negative is to be defined?

A basic definition of terms.

The non-native invader may provide different ecosystem services to the local life. Maybe more shade, but no nesting opportunities for migrating birds. Aliens may be better at storing or absorbing water but not provide foraging material.

It might seem favourable to have additional flora and fauna or fungi introduced to dry and arid landscapes, but desert ecosystems thrive through diversity and species are highly adapted to environmental conditions and each other (e.g. mutualism). This makes deserts resilient to significant changes and extreme climate and soil conditions. Once invasive species are introduced, they modify the equilibrium of the native ecosystem, resulting in native species being outcompeted, and altered soil conditions, seed bank, habitat and diversity. This can also result in denser vegetation that is more susceptible to fires that can spread rapidly.

Despite invasive species challenging the ‘locals’ survival and growth, some can coexist with limited impact, and this is described as environmental fluctuation and other coexistence mechanisms. Empty ecological niches, additional or underused nutrients, water availability (unlikely in the desert, right?) and the absence of native species that can thrive well under the combination of conditions. As a result,

Environmental engineering in the Anthropocene

Humans alter natural systems on purpose and as secondary effects of other actions (disturbance) and are unaware of their impact in some cases. On an environmental level, the deliberate introduction of predator species for native pest-manage (the cane toad story) is a well-known example. So how can we judge if an introduction or non-native reforestation effort in desert environments has a dominating positive effect or if species turn invasive and damage local ecosystems?

In addition, “”fitness-density covariance”” is described as where both native and invasive species increase their populations when the conditions are favourable. So, invasive species have a negative impact overall on ecosystems, but there are instances whereby species can coexist and thrive. The idea that alien annuals may exploit different seasons compared to locals seems unlikely as evolutionary adaptation has taken place over millennia.

Invasive species and climate change

Climate change, drought, extreme weather events, and heat waves are increasing globally. Deserts are not an exception. This additionally alters environmental equilibriums. Native species may be driven to the brink of their climatic tolerance, creating a competitive advantage for more robust aliens. In specific ecosystems, when exposed to drought and increased temperatures, native plants die as opposed to the invasives that recover from the stress and return in smaller numbers.dIn addition, human efforts to engineer resilient ecosystems may introduce new species trials and re-arrange specific communities. Utilising plants in semi-natural settings that previously only survived if nurtured now may naturalise because of reduced temperature stress.

The synergy of biological invasions and climate change is likely to increase the impact of invasive species on the desert environment and ecosystems. Even if the landscape is poor in terms of ecosystem services and habitat compared to tropical climates, they are ‘home’ to diverse, fragile and uniquely adapted communities of specialists that may be exploiting a very reduced niche or may be indigenous to a small geographic area. Of course, native species can bring some positives, such as habitat improvements and soil amelioration, but on the whole, ecosystems and biodiversity are altered and significantly impacted by invasive species.

Is homogenisation of biodiversity and ecosystem, similar to human migration, unavoidable? Can efforts to engineer ecosystems with sufficient awareness and in-depth research prevent irreversible losses in species?