‍The impact of niche construction on diversity

Organisms do considerably more in ecosystems than compete with and eat each other  (trophic interactions). They also produce, modify, and destroy habitat and resources, in the process driving co-evolution and regulating hydrological, nutrient, and element (e.g., carbon) cycling (Odling-Smee et al. 2003). Through niche construction and ecosystem engineering, organisms create ‘engineering’ control webs that affect the stability and productivity of ecosystems (Jones et al. 1994, 1997).

Across scales that encompass both the presence and absence of ecosystem engineering/niche construction, the net effect should be to enhance species richness via a net increase in habitat diversity (Jones et al. 1997). Recent studies provide support for this hypothesis. For example, natural sites with and without beavers exhibit low overlap in species composition. By increasing habitat heterogeneity, beavers increased herbaceous plant species numbers by more than 33% (Wright et al. 2002).

Another example is seaside arrowgrass (Triglochin maritima), which facilitates plant diversity in salt marshes by creating elevated rings (maintained structurally by its rhizomes) with increased reductive potentials and reduced salinity. T. maritima supports both a greater abundance of species and the growth of species not present in the adjacent substratum (Fogel et al. 2004).

Brathen & Raivolainen (2015) show that in tundra plant communities, forbs and grasses were the least abundant growth forms, yet they had a strong positive effect on species diversity through their effects on ecosystem process rates and nutrient cycling. The effects of these plants are completely disproportionate to their share of biomass.

Niche construction and conservation strategies

Findings like these have important implications for understanding, managing, and conserving ecosystems (Crain & Bertness 2006; Boogert et al. 2006; Laland & Boogert 2010).  Academics and politicians alike have failed to consider fully both the important role that these control webs play in ecosystems, and the consequences of human activities that destroy those webs of connectance.

If ecosystems are threaded by ‘engineering’ control webs, then the disappearance of key niche constructors may lead to abrupt changes in the resources and selection created by them, greatly affecting other species. Populations that have become dependent on engineered habitat and resources may be unable to cope with the loss, while genetic adaptation across generations is often too slow to counteract environmental modifications, leading to further declines in biodiversity and ecosystem functioning. This highlights the importance of preserving species that construct or maintain habitat and resources for other species (Crain & Bertness 2006; Boogert et al. 2006; Ehlers et al. 2008).

One might avoid unforeseen negative consequences of introducing engineering species by replenishing the niche constructors’ effects on the environment, rather than the organisms themselves (Odling-Smee et al. 2003). Some examples of the mimicking of engineering effects include introduction of artificial mussel mats (Crooks & Khim 1999), artificially created leaf ties otherwise produced by caterpillars (Lill & Marquis 2003), and relocalization of natural structures to provide lizard refuges (Pringle 2008). Research is required to explore the extent to which these manipulations can be successful, affordable and feasible at scales relevant to conservation goals.

Boogert et al. (2006) suggest an implementation strategy to conserve ecosystems through the conservation of niche-constructing activities. The strategy includes the following steps:

Step 1) Set conservation goals for the target ecosystem.

Step 2) Determine the key engineers in the target ecosystem, which will often require additional research.

Step 3) Conduct pilot studies to explore which of the following procedures might be most feasible and effective: (a) enhancing key engineers’ current activity by introducing more conspecifics or providing them with the resources required for population growth, (b) enhancing key engineering activities by introducing different species that engineer in the same manner, (c) introducing artificially manufactured products of the key engineers, and (d) creating optimal levels of abiotic and biotic factors to facilitate key engineers through trophic or nontrophic links. When the ecosystem is negatively affected by invading engineers, one could investigate the effectiveness of equivalent steps to reduce their impact.

Step 4) Implement the optimal engineering strategy or combination of strategies on a small scale. Follow up by monitoring and assessment.

Step 5) If step 4) has the desired outcome, implement the successful engineering strategy on a large scale.

Niche construction and the Anthropocene

Unlike any other species in Earth’s history, human niche construction is so potent that we have gained the capacity to transform the functioning of an entire planet (Ellis 2015; Waters et al. 2016).

Though contemporary rates and scales of anthropogenic environmental change are unprecedented, human societies began transforming Earth’s ecology many thousands of years ago (Smith & Zeder 2013; Boivin et al. 2016).

Anthroecology theory holds that human societies scaled up and gained the capacity to transform Earth’s functioning through a long-term evolutionary process, in which increasing societal scales and increasingly transformative ecosystem engineering are coupled through positive feedbacks (known as ‘runaway sociocultural niche construction’) (Ellis 2015, Ellis 2018).

Much attention has been given to how human activities can have a negative impact on biodiversity, and rightly so, but it is important to recognize that human impacts have multitudinous, complex and often conflicting effects on the biosphere. Counter-intuitively, recent research shows that human niche construction is actually increasing biodiversity in restricted contexts. For instance, it is known that a complex ecosystem of attached organisms develops on submerged structures (such as oil rigs) in the marine environment, which supports a localized food web that could not exist without them (Fortune & Paterson, 2018). The impact of human activity on the environment needs to be assessed on a case-by-case basis, drawing on careful science.