Physics aims at a fundamental understanding of our physical (material) world. Much of classical physics thereby either looks at far-away worlds like elementary particles and our universe, or it is geared towards eventual industrial applications like quantum computing. In contrast, with CCEES we aim to understand our nearby environment, still from a fundamental perspective and with the ultimate goal to understand how "more is different".

Environmental systems are different in that they invariably consist of many, often nonlinear subsystems that interact in a non-trivial way and across different scales. With this, a typical system of interest exhibits properties that are qualitatively different from those of any of its subsystems. These properties are called emergent. Elementary examples include the slope of a heap of sand and the size-distribution of its avalanches. At the complicated, and open end, is the bifurcation into physical environment and life, and their subsequent coevolution and further bifurcations.

Physical environmental systems are further complicated by their coupling with our sociocultural environment, an aspect that has increased over the past few thousand years, most dramatically through technological developments over the past half century that led to global-scale modifications of land use and climate.

Our approach in studying CCEES is to explore systems from widely different fields and to uncover the basic principles that command the development and evolution of phenomena at ever larger scales. Operationally, we develop, run, and analyze numerical simulations that are inspired by published experimental and observational studies on the different systems.

We currently operate in four main fields:

Chaotic Dynamics

Deterministic chaos is the tombstone on the simple-minded concept of "we just need to understand the parts with sufficient accuracy to predict the whole". As a representation of real environments, however, chaotic systems are way too simplified. They still provide useful playgrounds for conceptual studies that range from methods of data assimilation to stochastic control in environmental engineering.

The current work crew: Philipp Geier

Geomorphology

Land surfaces exhibit a plethora of forms including mountain ranges, river systems, deserts, savannas, forests, and all the way to agricultural and urban landscapes. Despite the diversity of these systems, some fundamental principles shine through. These include critical slopes (e.g., mountain slopes, alluvial fans, and sand dunes), patterned ground (e.g., crack networks and mud boils), and patterned vegetation (e.g., tiger bush). Besides their aesthetics and our fascination with such engineer-less regularity, these landscape structures play key roles in the land-atmosphere coupling as well as in the structuring of habitats and the corresponding coupling between competing animal and plant populations. In addition to mechanisms and phenomenologies, a key question is the resilience of such systems against instantaneous, continuous, or periodic perturbations.

The current work crew: Mathis Fels, Hendrik Leusmann, Julian Weninger

Population Dynamics

Life is certainly the most spectacular aspect of our physical environment and it plays a decisive role in the formation, maintenance, and transformation of our world. From an abstract perspective, life may be envisaged as a strongly connected, multiscale and multilevel network with the individual living beings as its elementary constituents. These constituents are structured in a complicated and hierarchical manner all the way to their biomolecular basis, and their lifetime is finite. The organization of life is mirrored in its dynamics, which covers a wide range of scales in time, space, and structure.

We focus on highly simplified aspects that include the temporal dynamics of small networks of species and their distribution and organization in spatially extended environments. These environments may be structured themselves with their dynamics eventually coupled with that of the population. As a further aspect, we study the development of such systems with a shifting or fluctuating environment.

The storylines for our abstract work include vegetation and large animals, microbial environments, gene environments, even chemical reaction systems, and they will reach out into economics and sociodynamics, eventually.

The current work crew: Long Huang, Bernhard Klein, Christian Schoder

Evolution

A key property of life is its capability to adapt to its environment, and to modify it. Mechanisms range from the flexibility of the individual beings through shifting weights in an existing gene-pool to the emergence of new species. This leads to an ever increasing efficiency in the exploitation of given resources, facilitates the quick adaptation to environmental changes, and, on long time-scales, forms our very environment.

Evolution is predominantly understood as the emergence of new biological species. The underlying mechanisms and the resulting phenomena are not particular to biology, however. They can be observed in any sufficiently complex system with handy examples in our technology as well as in our society.

Our research aims at understanding the relations between animate and inanimate aspects of the environment, their joint operation, and their coevolution. The corresponding framework in addition opens new perspectives in completely different fields, which we in particular explore for data assimilation.

The current work crew: Benjamin Herdeanu, Norbert König, Harald Mack, Yunus Sevinchan