Rapid climate change is forcing fundamental changes in the stewardship of protected areas. Emissions of greenhouse gases (primarily carbon dioxide, CO2) into the atmosphere have led to increases in global temperatures of 1.1°F (0.6°C) over the past 50 years (IPCC 2007). Warming trends are expected to exacerbate the effects of other ecosystem stressors, such as air pollution, exotic species (including introduced diseases), and disruptions of historical disturbance regimes. Much greater impacts from climate change are almost certain in coming decades, although predicting the exact conditions for a particular location is beyond our ability.
How should we manage natural areas in the face of these threats? It may be possible to encourage landscapes that can adapt to change (e.g., by altering fire management practices; Nydick and Sydoriak 2011) or are better able to withstand changing conditions (for examples see Millar et al. 2007). At the same time it is becoming increasingly important to prevent natural areas from contributing to greenhouse gas emissions. This represents an aspect of mitigation that may be new to National Park Service (NPS) managers, and one that could fit into the NPS Climate Change Response Strategy (NPS 2010).
It is becoming increasingly important to prevent natural areas from contributing to greenhouse gas emissions.
Terrestrial ecosystems store vast amounts of carbon, on the order of 2,200 to 2,800 billion tons C (2,000 to 2,500 billion Mg; 1 Mg = 1 megagram = 106 g = 1 metric ton) (Houghton 2007). By comparison, the atmosphere is estimated to contain approximately 880 billion tons C (800 billion Mg C). Much of the terrestrial carbon is found in soil and is relatively insensitive to most, but not all, land management practices occurring in national parks (see “Road removal” below). But in some terrestrial ecosystems, particularly forests, a large proportion of ecosystem carbon is stored in vegetation (Bonan 2008). The carbon pool (or “stock”) held in live vegetation is vulnerable to sudden release following major disturbances such as drought, insect outbreaks, and fire (Kurz et al. 2008). As live vegetation dies and decomposes, the carbon held in once-living biomass is eventually released back into the environment and contributes to further climatic changes. Protecting forested landscapes in national parks is especially important, as some of these sites may hold extremely large amounts of carbon (e.g., old-growth forests).
Reducing greenhouse gas emissions in national park operations is already a priority (e.g., NPS Climate Friendly Parks Program), but managing ecosystem carbon stocks is a relatively new consideration. In some cases maintaining carbon stocks will be in direct conflict with other management goals, for example removing invasive species such as tamarisk and Russian olive trees, which may contain substantial carbon. Often, the connection between management actions and their ultimate effects on carbon stocks is less clear. For example, prescribed fire may directly release large amounts of CO2 via combustion and tree mortality. But burning may result in a landscape more resistant to future wildfire, which could otherwise release large amounts of carbon (this carbon accounting may not apply over large scales; see Campbell et al. 2011). Considering management outcomes for carbon stocks is likely to become more common in the future, but tools necessary to do so are still under development.
A first step in understanding management effects on ecosystem carbon stocks is to inventory and monitor these stocks, although they are notoriously difficult to measure. Given limited budgets and staff, how can park managers assess ecosystem carbon stocks and their changes over time? In this case study we present our estimates of ecosystem carbon stocks in soils and vegetation at Redwood National and State Parks (“the parks”), California. We also consider changes to these stocks directly linked to park management (and some of the uncertainties associated with our estimates). We describe the methods we used with the intention that our work might be useful to managers interested in similar assessments.
van Mantgem, P., M. A. Madej, J. Seney, and J. Deshais. 2013. Estimating ecosystem carbon stocks at Redwood National and State Parks. Park Science 30(1):1,20–26.
Available at http://www.nature.nps.gov/ParkScience/archive/PDF/Article_PDFs/ParkScience30(1)Summer2013_1_20-26_van_Mantgem_et_al_3643.pdf.