Complexity and the Biosphere

Te Pūnaha Matatini is applying network analysis, complexity theory, and dynamical systems methodologies to understand the biosphere; developing models that couple the interactions between biodiversity, the economy, and human decision-making.

The diversity of life on Earth is the planet’s most striking feature; recent estimates are that fewer than a million of approximately eight million animal species have been described. Biodiversity exists at a large range of physical scales: multicellular eukaryotes have linear dimensions that range in size from tens of microns to tens of metres, and metazoans encompass 17 orders of magnitude by volume. The ability of next generation sequencing technologies to efficiently and simultaneously analyse massive numbers of DNA molecules has allowed the diversity and ecology of microbial communities to be examined in previously unfeasible depth and detail. This vast new resource for understanding the hidden majority of species that contribute to New Zealand’s terrestrial ecosystems and ecosystem services will require new tools for its analysis and visualization. The research in this theme will inform government policy and decision-making, and will assist the New Zealand public in better understanding their relationship with our unique flora and fauna.

Projects:

Predator-free New Zealand

“It’s crazy and ambitious but I think it might be worth a shot.” is how the late Sir Paul Callaghan popularised the idea of a New Zealand free of exotic pests. The challenges in realising this vision include sampling methods for detection at low densities, economic questions on the worth of predator-free and who would benefit, the social relationships with hunting lobby groups and fur harvesters, and logistics of how it could be achieved. Combining economic models with ecological modelling and epidemic models, we will undertake a systematic cost-benefit analysis of predator-free versus long-term control to identify its overall economic viability, to identify particular regions and pests that would give the best economic impact, and to identify appropriate incentives for businesses to become involved. Community engagement is crucial to eradication success as exemplified by the possum-free Miramar peninsula. We will develop a smart phone application that allows the general public to report the locations of pest sightings and collect data on pest levels. We will then establish methods to compare this crowd-sourced data to known predator levels from existing surveys, and incorporate this data into models to make predictions and test various management strategies

Three-year outcome: a rigorous cost-benefit analysis of the benefits of ecosystem function after large-scale predator control

Reconciling biological and economic values of our marine food resources

Marine fisheries are a critical global resource of the 21st century but under considerable threat from intensified harvesting, climate change, and human-induced pollution. Understanding the structure and dynamics of complex marine ecosystems alone will be insufficient for preserving them; knowledge of the interdependencies and interactions between these resources, direct and indirect cultural activities, and changing background climate is crucial for effective long-term ecosystem management and resource sustainability. New Zealand struggles to combine local cooperative approaches to management with the formal regulation of harvests and almost universally, regulated extant fisheries (commercial and recreational) are highly selective in targeting specific species and size ranges. There is an increasing amount of research pointing to alternative strategies and the impacts that these have on fisheries. New Zealand has detailed data on commercial harvests for over 25 years that we can use to explore current management systems but ecological and social processes operate over much longer temporal scales. Extant ecological and economic studies typically offer little more than half-century perspectives on marine fisheries trends and outcomes. To complement these, archaeological datasets provide an opportunity to achieve century and multi-century scale perspectives on complex interactions between ecological, sociocultural, and climatological systems, and the co-evolution of network structures and dynamics. We propose to examine long-term resilience in North Island New Zealand fisheries at both artisanal and commercial scales, using a combination of contemporary and historical records (archaeological, ethno-historical) and mathematical and agent-based models.

Three-year outcome: a robust model of how different aspects of human behaviour and interactions affect ecological indicators of the health of fisheries that is used to inform fisheries management policy

Epidemic spread

Infectious diseases can be either good or bad: bad in that they can adversely affect human populations, but good in that these same effects on a pest population can dramatically aid in pest control. Both effects, good and bad, are merely different facets of the complex behaviour that emerges in the epidemiology of an interacting population. A striking annual example is the arrival to New Zealand shores each year of Influenza and other winter-only seasonal illnesses. Every year multiple types and subtypes of human Influenza virus arrive in New Zealand at the beginning of the winter season. These seasonal epidemics are established from a small number of infected individuals arriving early in the season and the epidemic subsequently spreads through human-to-human contact and proximity, following human networks. Quantitative studies of infectious diseases that incorporate demographic variations through lifestyle, biophysical, and socio-economic factors are crucial both for understanding how diseases can be controlled or propagated. When an infection disease is introduced into the population, this heterogeneity is increased as the disease affects people differently, which can have a striking effect on the spread of a disease through a network of individuals. This project will aim to develop models of disease spread on a network that take into account these individual characteristics, quantify their effect on disease spread and identify possible methods for epidemic control. Data from the spread of TB in the possum population of the Orongorongo valley combined with full contact tracing data from this population will allow for parameterisation and verification of the models developed. With this population in mind the project will establish methods not only to contain the spread of a disease but also to promote its spread through a given population. Results from this second case will be vital if New Zealand decides to use bio-control methods to control the possum population.

Three-year outcome: A regional-level model of an acute airborne infectious disease spreading through New Zealand, which can be used to inform healthcare response, and a suite of bio-control methods that could be used to control the possum population.