Mark A. Harwell

Climate Change Impacts on U.S. Coastal and Marine Ecosystems

Increases in concentrations of greenhouse gases projected for the 21st century are expected to lead to increased mean global air and ocean temperatures. The National Assessment of Potential Consequences of Climate Variability and Change (NAST 2001) was based on a series of regional and sector assessments. This paper is a summary of the coastal and marine resources sector review of potential impacts on shorelines, estuaries, coastal wetlands, coral reefs, and ocean margin ecosystems. The assessment considered the impacts of several key drivers of climate change: sea level change; alterations in precipitation patterns and subsequent delivery of freshwater, nutrients, and sediment; increased ocean temperature; alterations in circulation patterns; changes in frequency and intensity of coastal storms; and increased levels of atmospheric CO2. Increasing rates of sea-level rise and intensity and frequency of coastal storms and hurricanes over the next decades will increase threats to shorelines, wetlands, and coastal development. Estuarine productivity will change in response to alteration in the timing and amount of freshwater, nutrients, and sediment delivery. Higher water temperatures and changes in freshwater delivery will alter estuarine stratification, residence time, and eutrophication. Increased ocean temperatures are expected to increase coral bleaching and higher CO2 levels may reduce coral calcification, making it more difficult for corals to recover from other disturbances, and inhibiting poleward shifts. Ocean warming is expected to cause poleward shifts in the ranges of many other organisms, including commercial species, and these shifts may have secondary effects on their predators and prey. Although these potential impacts of climate change and variability will vary from system to system, it is important to recognize that they will be superimposed upon, and in many cases intensify, other ecosystem stresses (pollution, harvesting, habitat destruction, invasive species, land and resource use, extreme natural events), which may lead to more significant consequences.

Indicators of Ecosystem Recovery

Assessment of ecological changes relative to disturbance, either natural or human-induced, confronts a fundamental problem. Ecosystems are complex, variable, and diverse in nature; consequently, the need for simplification to essential features that would characterize ecosystems adequately is generally acknowledged. Yet there is no firm prescription for what to measure in order to describe the response and recovery of ecosystems to stress. Initial focus is provided by identifying relevant ecological endpoints, i.e., ecological changes of particular relevance to humans. Furthermore, we suggest generic purposes and criteria to be considered in making choices of ecological indicators that relate to those endpoints. Suites of indicators, with variety of purposes, are required to assess response and recovery of most ecosystems and most stresses. We suggest that measures of certain ecosystem processes may provide special insight on the early stages of recovery; the use of functional indicators as complimentary to other biotic indicators is highlighted in an extended example for lotic ecosystems.

Use of general circulation model output in the creation of climate change scenarios for impact analysis

Many scientific studies warn of a rapid global climate change during the next century. These changes are understood with much less certainty on a regional scale than on a global scale, but effects on ecosystems and society will occur at local and regional scales. Consequently, in order to study the true impacts of climate change, regional scenarios of future climate are needed. One of the most important sources of information for creating scenarios is the output from general circulation models (GCMs) of the climate system. However, current state-of-the-art GCMs are unable to simulate accurately even the current seasonal cycle of climate on a regional basis. Thus the simple technique of adding the difference between 2 × CO2 and 1 × CO2 GCM simulations to current climatic time series cannot produce scenarios with appropriate spatial and temporal details without corrections for model deficiencies.In this study a technique is developed to allow the information from GCM simulations to be used, while accommodating for the deficiencies. GCM output is combined with knowledge of the regional climate to produce scenarios of the equilibrium climate response to a doubling of the atmospheric CO2 concentration for three case study regions, China, Sub-Saharan Africa and Venezuela, for use in biological effects models. By combining the general climate change calculated with several GCMs with the observed patterns of interannual climate variability, reasonable scenarios of temperature and precipitation variations can be created. Generalizations of this procedure to other regions of the world are discussed.

A Framework for an Ecosystem Integrity Report Card

543 E cosystem management is a structured process for society to define what ecological condition is desired at each part of a region and to develop and implement management policies designed to achieve that mosaic of desired sustainable ecological conditions (US MAB 1994, IEMTF 1995a, 1995b, Christensen et al. 1996, Harwell et al. 1996, Harwell 1998). Ideally, the establishment of ecological goals involves a close linkage between scientists and decision makers, in which science informs decision makers and the public by characterizing the ecological conditions that are achievable under particular management regimes, and decision makers make choices reflecting societal values, including issues of economics, politics, and culture. Because ecosystem management is adaptive—that is, management is adjusted if necessary to achieve goals—the general public, the scientific community, resource managers, and decision makers need to be routinely apprised of progress toward achieving the desired ecological goals, that is, they need a “report card” on ecosystem condition or integrity. The concept of report cards or performance measurements to describe progress toward environmental goals has evolved over the past few decades as environmental legislation and the appropriation of public funds for environmental restoration, preservation, and management have increased. Over this time, reports have expanded from measurement of the effects of single initiatives (e.g., land acquisition goals for parks and protected areas) and progress toward pollution reduction in single media (e.g., reduction of air or water emissions) to encompass the broader and longer-term regional ecosystem management and restoration approaches that have been developing in highly valued ecosystems throughout the country (e.g., the Greater Everglades, San Francisco Bay, Chesapeake Bay, the Great Lakes, and the Pacific Northwest). These holistic, often multi-agency efforts to maintain accountability for regional ecosystem integrity and the progress of restoration activities stem in part from the proactive desire of resource managers to maintain public interest, support, and, consequently, funding for long-term environmental restoration and management efforts. They also stem in part from specific legislative or regulatory requirements to engage the public in the ecosystem management process (e.g., EPA/EC 1995, 1996, Chesapeake Bay Program 1996, NSTC 1996a, 1996b) or from direct requests from Congress, A Framework for an Ecosystem Integrity Report Card

The natural South Florida system I: Climate, geology, and hydrology

Developing hypotheses for sustainability requires an understanding of the natural forces that shaped the historical Everglades prior to extensive engineering of the landscape. The historical Everglades marsh covered 10,000 km2 in a 100-km-long basin that has an extremely low gradient (slope of only 3 cm · km-1). The region is characterized by a heterogeneous landscape that has developed over the past five millennia, functioning as an interconnected mosaic of wetland, upland, estuarine, and marine ecosystems. The boundaries of this system were defined as the historic drainage basin from the Kissimmee River system through Lake Okeechobee, the Everglades, Florida Bay, and out through the Florida Keys to the coral reef tract. This geographic area is interconnected through the regional hydrology, with its unifying surface and subsurface freshwater transport system. However, in the final analysis, the interaction of geologic and climatic processes determine the systems hydrology, a major determinant of community and landscape structure and the point of connectivity between natural and human systems. This review examines the role of climate, geology, soils and sediments, topography, and hydrology in shaping and modifying ecological systems through time. However, it is clear from the wetland nature of this system that the predrainage hydrologic features were critical to the sustainability of the Everglades. Important hydrologic features include sufficient water quantity, storage, and sheetflow, and the appropriate hydroperiod and timing of water releases over both annual and interannual variations in precipitation.

Ecosystem management to achieve ecological sustainability: The case of South Florida

The ecosystems of South Florida are unique in the world. The defining features of the natural Everglades (large spatial scale, temporal patterns of water storage and sheetflow, and low nutrient levels) historically allowed a mosaic of habitats with characteristic animals. Massive hydrological alterations have halved the Everglades, and ecological sustainability requires fundamental changes in management.The US Man and the Biosphere Human-Dominated Systems Directorate is conducting a case study of South Florida using ecosystem management as a framework for exploring options for mutually dependent sustainability of society and the environment. A new methodology was developed to specify sustainability goals, characterize human factors affecting the ecosystem, and conduct scenario/consequence analyses to examine ecological and societal implications. South Florida has sufficient water for urban, agricultural, and ecological needs, but most water drains to the sea through the system of canals; thus, the issue is not competition for resources but storage and management of water. The goal is to reestablish the natural system for water quantity, timing, and distribution over a sufficient area to restore the essence of the Everglades.The societal sustainability in the Everglades Agricultural Area (EAA) is at risk because of soil degradation, vulnerability of sugar price supports, policies affecting Cuban sugar imports, and political/economic forces aligned against sugar production. One scenario suggested using the EAA for water storage while under private sugar production, thereby linking sustainability of the ecological system with societal sustainability. Further analyses are needed, but the US MAB project suggests achieving ecological sustainability consistent with societal sustainability may be feasible.

Indicators of Ecosystem Response and Recovery

To facilitate effective protection of environmental systems subjected to anthropogenic activities, there must be basic understanding of three areas: how the variety of biological components of ecosystems are exposed to stress; how the ecosystems respond to that disturbance; and how they recover or adapt. Given a solid understanding of ecosystem exposure-response-recovery relationships and their uncertainties, we might reasonably balance risks to ecological systems with risks and benefits to other systems of human concern, such as economic or societal systems. While the approach to the problem seems straightforward, the simple fact is that we presently lack sufficient ecological understanding in all three areas for most environmental stresses. With limited ability to make reliable stress-response predictions, we are greatly constrained in making appropriate environmental decisions. Consequently, instances of unexpected, adverse effects on the environment from a particular human activity continue to intermingle with instances of expensive over-protection from other activities. In principle, ecological risk assessment would minimize these problems.

SCIENCE AND ENVIRONMENTAL DECISION MAKING IN SOUTH FLORIDA

The ecosystems of South Florida are unique and highly valued by society. Explosive population growth this century has made the Everglades one of our nation’s most endangered ecosystems. The dominant anthropogenic stressor is hydrological modifications instituted to provide flood protection for land selected for agriculture and urban development. Thus, major redesign of the hydrologic system is essential if the Everglades and associated coastal ecosystems of South Florida are to be restored and sustained. Following conceptual frameworks developed for ecological risk assessment, ecological sustainability, and ecosystem management, the U.S. Man and the Biosphere Human-Dominated Systems Directorate has conducted a project on ecosystem management in South Florida. An extremely complex hierarchy of federal, state, and local governmental activities presently underway is directed toward a sustainable South Florida. The scientific community is playing a significant role in this process, but the success or failure ...

Ecosystem Management of South Florida Developing a shared vision of ecological and societal sustainability

and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149. He is an ecosystems ecologist specializing in methods for ecological risk assessment and ecosystem management. He is also chair of the US Environmental Protection Agency Science Advisory Board (SAB) Ecological Processes and Effects Committee and chair of the US Man and the Biosphere Program (US MAB) Human-Dominated Systems Directorate. The time has come to

POTENTIAL EFFECTS OF GLOBAL CLIMATIC CHANGE ON THE PHENOLOGY AND YIELD OF MAIZE IN VENEZUELA

Simulated impacts of global and regional climate change, induced by an enhanced greenhouse effect and by Amazonian deforestation, on the phenology and yield of two grain corn cultivars in Venezuela (CENIAP PB-8 and OBREGON) are reported. Three sites were selected:Turén, Barinas andYaritagua, representing two important agricultural regions in the country. The CERES-Maize model, a mechanistic process-based model, in theDecision Support System for Agrotechnology Transfer (DSSAT) was used for the crop simulations. These simulations assume non-limiting nutrients, no pest damage and no damage from excess water; therefore, the results indicate only the difference between baseline and perturbed climatic conditions, when other conditions remain the same. Four greenhouse-induced global climate change scenarios, covering different sensitivity levels, and one deforestation-induced regional climate change scenario were used. The greenhouse scenarios assume increased air temperature, increased rainfall and decreased incoming solar radiation, as derived from atmospheric GCMs for doubled CO2 conditions. The deforestation scenarios assume increased air temperature, increased incoming solar radiation and decreased rainfall, as predicted by coupled atmosphere-biosphere models for extensive deforestation of a portion of the Amazon basin. Two baseline climate years for each site were selected, one year with average precipitation and another with lower than average rainfall. Scenarios associated with the greenhouse effect cause a decrease in yield of both cultivars at all three sites, while the deforestation scenarios produce small changes. Sensitivity tests revealed the reasons for these responses. Increasing temperatures, especially daily maximum temperatures, reduce yield by reducing the duration of the phenological phases of both cultivars, as expected from CERES-Maize. The reduction of the duration of the kernel filling phase has the largest effect on yield. Increases of precipitation associated with greenhouse warming have no effects on yield, because these sites already have adequate precipitation; however, the crop model used here does not simulate potential negative effects of excess water, which could have important consequences in terms of soil erosion and nutrient leaching. Increases in solar radiation increased yields, according to the non-saturating light response of the photosynthesis rate of a C4 plant like corn, compensating for reduced yields from increased temperatures in deforestation scenarios. In the greenhouse scenarios, reduced insolation (due to increased cloud cover) and increased temperatures combine to reduce yields; a combination of temperature increase with a reduction in solar radiation produces fewer and lighter kernels.