Maximizing empower on a human-dominated planet: The role of exotic Spartina

Maximizing empower on a human-dominated planet: The role of exotic Spartina Daniel E. Campbell a , Hong-Fang Lub,∗ , George A. Knoxc , Howard T. Odumd,1 a USEPA, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Atlantic Ecology Division, Narragansett, RI, USA b South China Botanical Garden, Chinese Academy of Sciences, Le Yiju, Guangzhou, Guangdong 510650, China c Canterbury University, Christchurch, New Zealand d University of Florida, Gainesville, FL, USA article info Article history: Received 1 May 2008 Received in revised form 15 July 2008 Accepted 24 July 2008 Keywords: Exotic Spartina Emergy analysis Energy Systems Theory Maximum empower Human-dominated planet Salt marshes abstract The emergy signature of the earth has changed dramatically over the past 250 years as a result of the development of technologies to use fossil fuels for human purposes. This change has resulted in the self-organization of modern industrial societies and their concomitant processes now dominate the earth. One such process is the transport of species from specific regions of the Earth, to which they were formerly confined, and their introduction to new territories. In this paper, we examine the role of exotic Spartina sp. in promoting the self-organization of coastal ecosystems for maximum empower on three coasts, Marlborough Sounds, NZ, Willapa Bay, WA, USA and Jiangsu Province, PRC. We found evidence to support the hypothesis that Spartina marsh maximizes empower through the building of new land in coastal environments that are dominated by an excess of sediment. Where excess sediments are present as a consequence of past geologic processes, and where a low marsh plant was absent, Spartina has been seen as an interloper to be destroyed. There is some evidence that given sufficient time, exotic Spartina marshes may increase productivity and diversity in these coastal systems, as well as those that are actively prograding. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The Earth has undergone a change of state over the past 250 years. This change has been characterized first by the development of industrialized societies and then by the rise of the information age with its concomitant use of complex technologies. As a result, in the present time lights seen from space at night (Plate 1) show that human beings occupy and to a large extent control a large fraction of the surface of the earth, as evidenced by the lighted areas which demarcate cities and towns devoted, almost entirely, to human uses. Human control of the earth is manifested through the alteration of the ∗ Corresponding author. Tel.: ; fax: . E-mail address: (H.-F. Lu). 1 Deceased. magnitude, speed and sometimes the nature of energy, material and information fluxes of the biogeosphere (Vitousek et al., 1997). The new patterns of energy and material flux require new structures to develop maximum empower (Lotka, 1922a,b; Odum, 1996; Campbell, 2001) through the altered ecological networks. In this paper, we consider how the transfer and development of biological information, in the form of exotic Spartina species, provides new ecological structures that are the basis for maximizing empower in systems where the flows of sediment have been radically altered by human activities and in other systems where a low salt marsh species with Spartina’s tolerance for inundation was formerly absent. The /$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/ng.2008.07.022 464 ecological engineering 35 (2009) 463–486 Plate 1 – Earth at Night, 27 November 2000. Credit: C. Mayhew and R. Simmon (NASA/GSFC), NOAA/NGDC, DMSP Digital Archive. social and political reactions to the growth of exotic Spartina were examined and the ecological and social outcomes that have resulted from people’s actions to control or manage exotic Spartina were compared to the ecological role of the plant. 1.1. Origin and characteristics of industrial civilization The rapid industrialization of the earth was made possible, because human beings developed the technological expertise to utilize the vast quantities of fossil energy stored within the earth. Coal, oil, and petroleum natural gas had been accumulating beneath the earth for many millions of years up to 1769 when James Watt patented his improvements to the Newcomen steam engine. Watt’s improved engine opened the way to the wide spread use of coal to produce steam power that ignited the industrial revolution in England and the world. By 1850 coal had become a discernable source of energy for the U.S. (EIA, 2008) and around 1885 it became the largest energy source used by the United States. As a result of the rapid increase in industrial development afforded by coal-power, planetary material flows and processes began to change. One of the chief characteristics of the aggregation of people into societies is that the natural material cycles of the earth are broken and rearranged into an alternate pattern (Odum, 2000). The extraction of fuels and minerals from their stable stored states on or beneath the earth’s surface and the subsequent transportation of these materials to sites where they are used in some industrial process characterize this altered pattern. The by-product of creating refined and synthetic materials and the articles made from them is that some of the energy and materials used in the process inevitably become wastes. Ecosystems have adapted over many millions of years of evolution to minimize waste and to sequester harmful materials in places where they become chemically or biologically bound, and as a result, toxic materials are separated from most of the living world (Odum, 2000). For example, wetlands receive natural concentrations of toxic metals that have been concentrated from the landscape by water flows. Chemical processes in the wetland transform and sequester these materials in complexes where they are bound with organic matter, e.g., peat, sediment organic matter, etc., (Thurman, 1985) which is eventually buried in the earth. Through this process naturally occurring rare and toxic materials are removed from the habitats of most living organisms (Odum, 2000). The altered pattern of material flow required to support civilization results in highly concentrated waste materials being released in areas where the existing ecosystems are not adapted to process them effectively. 1.2. The altered sedimentary cycle and marsh growth Whereas human alternation of the earth’s material cycles can be easily demonstrated, if one considers the extraction, transportation, and refining of petroleum and critical materials like lead (Odum et al., 2000), phosphorus, and iron, it is perhaps not so evident with regard to the sedimentary cycle of the earth. Yet the earth’s sedimentary cycle has been greatly altered by human activities even prior to the industrial age. Before the industrial age, human societies were based primarily on agriculture and the muscle power of animals and people. The intense exploitation of regions for agricultural production was and is a primary cause of human alteration of the sedimentary cycle. Perhaps nowhere in the world is this more evident than in the Yellow River Basin of China, where hundreds of years of intensive agriculture resulted in enhancing the accumulation of sediments in a vast delta at the mouth of the river that has now become cut-off and submerged as a result of the river changing course (Zhang et al., 2002). The balance of sediment supply from the land and sea with the erosive forces of wind and water determines whether a coast will prograde or retrograde. Wherever sediments accumulate a substrate is available to support the growth of marsh grass. Once marsh grasses colonize open mudflats the process of building new land begins and it is accelerated by the feedback processes of marsh growth itself, by which the flow of sediment bearing flood waters is slowed as they pass through a dense sward of grass stems allowing particles to settle out and further increase deposition (Landin, 1991). The fact that it is sediment supply and not marsh growth that is the primary ecological engineering 35 (2009) 463–486 465 factor in land building can be seen by examining a microcosm of the process as it occurs along the coast of Maine in the United States (Kelley et al., 1988). Here steep coastal cliffs or bluffs regularly slump into the sea below, forming hillocks of sediment. This substrate is quickly colonized by Spartina alterniflora Loisel that consolidates the loose sediment into a small marsh. However, since slumping rarely occurs in the same area with regularity, the newly formed marsh is soon subjected to the erosive power of winter storms from the Gulf of Maine. Without a continuous supply of sediment the new marsh begins to erode and within a few years it is washed away, only to reform when sediments slump off of the bluff once again. This causal connection between sediment and salt marsh (Jacobsen et al., 1987; Kelley et al., 1988; Wood et al., 1989) is a good example of an Energy Systems Theory hypothesis that the signature of available energies and more exactly the emergy signature supplied to a place uniquely determines the ecological organization that develops there (Odum et al., 1977; Twilly, 1995; Campbell, 2000b, 2005; Campbell et al., 2005). 1.3. Emergy and transformity Before further considering the implications of this hypothesis to our study, we briefly introduce two key ideas derived from Energy Systems Theory (Odum, 1994), emergy and transformity, which are used in our analysis of exotic Spartina. Emergy is all the available energy of one kind used up directly or indirectly in creating a product or service in a natural or human system (Odum, 1996). If solar energy is used as the base for determining the emergy contained in an item, the unit of emergy is the solar emjoule (sej), which connotes the past use of available solar energy required for the product’s formation (Scienceman, 1987). Solar transformity is the solar emergy (sej) required to produce a unit of available energy (J) in a product. Energy and emergy signatures can be produced for any location by first tabulating the available energies for a defined set of spatial boundaries and then determining the emergies that flow in over a defined time period. Next both energy and emergy are plotted separately against a set of categories arranged on the abscissa in order of increasing transformity (Odum, 1988). The plot of the magnitude of the available energy inputs by category is called the energy signature of the place and the plot of the magnitude of the emergy inputs is called the emergy signature. A flow of emergy (sej/unit time) is empower and the maximization of empower through a system network is the criterion for success in evolution proposed by the maximum empower principle (Odum, 1996). 1.4. Exotic Spartina and the response of ecosystems to change in their emergy signatures Energy Systems Theory hypothesizes that the structure of an ecosystem will alter to best use a new persistent suite of available energies, first by adaptation and then by evolutionary change for signatures that are stable for longer times (Fig. 1 and Campbell, 2000b). In the short term, systems first resist change and then respond dynamically to recover from perturbations, a property described as resilience by Holling (1973). Under emergy signature changes of longer duration ecosysFig. 1 – The major ecological processes acting over time in response to changes or perturbations of the emergy signature of a place. Resistance to change is seen in the first three points after the signature changes. Resilience is the process by which the system departs from and then recovers its original state. In the long run evolution leads to a new state with similar empower if the new signature contains this potential. tems may transition to a new stable state, which may differ from the original state in structure and function. All these responses are seen in the Earth’s ecosystems today (Campbell, 2000b), but here we are primarily concerned with the impetus for state change that is manifest along the coasts of the world. In this paper, we consider the ecological role played by exotic Spartina in three coastal systems that originally lacked a low marsh species with Spartina’s tolerance for inundation; (1) the coast of New Zealand (NZ), where Spartina × townsendii H. & J. Groves and Spartina anglica C.E. Hubbard were introduced to reclaim tidal lands for pasture, to protect shore lands, and stop bank erosion (Asher, 1991); (2) Willapa Bay, Washington, on the northwestern coast of the United States where S. alterniflora was accidentally introduced from the east coast (Boyle, 1991) with the oyster, Crassostrea virginica, which was brought to the bay when the native Pacific oyster population collapsed in the mid 1880s (Sayce, 1977); and (3) the Yancheng Biosphere Reserve on the coast of Jiangsu Province in China, where both S. anglica and S. alterniflora have been introduced for shoreline stabilization and land-building (Chung, 1994). 2. Theoretical considerations Often in the past, the evolutionary process is thought to have played out in relatively isolated regions over long periods of time under relatively stable emergy signatures. This isolation allowed flora, fauna and the ecosystems that they compose to slowly diversify and become adapted to the prevailing conditions as represented in the emergy signature of the place. The maximum empower principle (Lotka, 1922a,b; Odum, 1996) hypothesizes that the process of evolution is guided by a particular criterion, i.e., the emergy flow within networks that prevail is maximized. Thus, the trajectory of evolution is always toward developing greater empower for a given set of emergy inputs and as a result the production process for individual system components and processes proceeds towards the lowest possible set of transformities for the system (Odum, 1994; Campbell, 2000b). Apparently, this 466 ecological engineering 35 (2009) 463–486 Fig. 2 – The emergy signature of the Earth in 1850 and in 1995 using data from Brown and Ulgiati (1999). process of gradual change has been interrupted occasionally by extinction events impinging from larger scales of organization (Eldredge, 2008). The largest of these are mass extinctions that have caused rapid and drastic change (Alvarez et al., 1980) in the ecological organization of the earth. The emergy basis for the state change alluded to in the Introduction can be demonstrated by examining the emergy signature of the earth before and after the beginning of the industrial age demarcated for this purpose as 1850 (Fig. 2). The magnitudes of many of the earth’s material fluxes have undergone near exponential growth over all or part this time (Canadell and Mooney, 2002) following the growth of human populations and energy use. Changes in material and energy fluxes are seen to varying degrees on all scales of spatial organization corresponding to the magnitude of different human activities on the landscape, e.g., urbanization, agriculture, forestry, road building, etc. In addition, all major activities of human society have grown exponentially during this period. The exponential expansion of transportation is of particular interest in understanding the process by which life is adapting to the changes that our technological society has brought to the planet. In the past, geological events of great magnitude and high transformity, e.g., the emergence of the Isthmus of Panama, were responsible for the mass migration of species from one formerly isolated region to another (Simpson, 1940). These events provided a major test of existing patterns of system organization for maximum power and they provided an opening for changes to the old order (Mercer and Roth, 2003). Today, the growth of transportation systems has increased the flux of species through both directed and incidental introductions (see the Global Invasive Species Database, New species entering an area increase the floral and faunal information available to ecosystems altered by human activities and provide choices to support further self-organization there. Thus, a concomitant process caused by human activities that accompanies the expansion of global material and energy flows provides a greater variety of biological information (i.e., species) for the selection of pathways that maximize empower (Campbell, 2001) in these newly altered ecological systems. We hypothesize that the success or failure of an introduced species will be determined by the emergy signature that it encounters in its new environment. For example, the wide-spread human alteration of the pre-industrial emergy signatures of ecosystems from the local to the global scale has provided many opportunities for new species to enter existing system networks, while also creating some entirely new signatures that are the basis for the self-organization of new system networks. Also, some ecosystems are at less developed points in their trajectory toward maximum empower for their natural emergy signatures. These systems have possibilities for further self-organization that can be exploited by introduced species that were formerly isolated in other regions, but now are increasingly moved both intentionally and accidentally into new areas. Both of these co