Module 7: Ecosystems as Complex Systems

• CSS 


  complex systems science
• Ecological complexity provides emphasis on relationships between pattern & process in natural systems
• Ecological complexity is characterized by (1) local interactions between individual ecosystem components, (2) feedbacks between processes occurring at different scales, (3) amplification of minor variations in initial conditions, & (4) emergence of patterns in absence of global controller
• A good example of a complex system governed by laws of physics and chemistry is the ecosystem
• Emergent properties are patterns at higher levels emerging from localized interactions & selection processes acting at lower levels
• The global economy and our brain are examples of complex systems
• The four parameters of complexity are: elements, nonlinearity, connectivity, & autonomy
• Nonlinearity is where non-additive interactions and feedback loops over time give exponential relations between input & output to systems
• Connectivity appears as networks in a higher level that indicates the degree of how things flow in the network
• Autonomy & adaptation enable self-organization & process of evolution that shapes complex systems on macro scale
• Resiliency is achieved in the presence of alternative species due to connectivity
• The three dimensions in ecology where complexity is measured: spatial, temporal, and structural
• Spatial complexity is measured through the manner species are organized in a given geographical location
• Examples of sources of spatial complexity are species distribution and vegetation patterns
• Elevation is defined as the distance of your subject above a reference point (i.e. sea level)
• A heat map is a diagrammatic representation of data whose values are represented as colors
• Vegetation patterns can provide a degree of better ecosystem service like food security in the indicated areas of a local community
• Temporal complexity is derived from dynamics or changes in population, effects of changes in climate & weather, etc.
• Temporal complexity characterizes time series of different variables describing dynamics of a system
• Perturbations affect ecosystem stability & complexity resulting in unfavorable conditions
• Structural complexity refers to relationships within the ecosystem as exemplified by the food web and species interaction networks
• The case of Yosemite National Park is an example of temporal complexity
• Fragmented habitats limit the gene pool for a particular species
• Black dots called nodes represent an individual organism situated in a habitat patch
• The black lines called edges represent relations between two nodes
• A node connected to many other nodes is designated as a hub
• The node with a higher number of connections compared to other hubs is regarded as a high-degree node
• A graph or connectivity network is composed of a set of nodes & edges
• Scale-free networks are highly resistant to random disturbances but vulnerable to deliberate attacks on the hubs
• Edges represent the flow of energy from one node (element/component) to another
• The ecosystem is a network of many components whose aggregate behavior is due to & gives rise to multiple-scale structural & dynamical patterns
• Type 1 measures increase with increasing disorder in system in a linear manner
• Type 2 measure are of a convex function that assign highest scores to systems whose regularity lies at intermediate level
• Evapotranspiration provides better capability for a land to sustain life depending on the maximum amount of water regained per unit of water consumed
• Metropolises and small towns are examples of artificial ecosystems
• Feedback processes reflect the impact of pressures (anthropogenic/natural)
• Anthropogenic or natural pressures modify ecosystem structure that may be beneficial or detrimental to the biosphere
• Interactions of components result in observable changes experienced locally or globally
• Feedbacks indicate the consequences of emergent & global agents manifested in the local heterogeneous interacting components of the ecosystem
• Examples of positive feedback include climate change, disease outbreaks, and death