Plants | |
| Overview | | |
| This section describes trends in two of the major kingdoms of life on earth: the green plants of the Kingdom Plantae and the molds, lichens, and mushrooms of the Kingdom Fungi. Members of the plant and fungal kingdoms have both economic and ecological importance. Plants transform solar energy into usable economic products essential in our modern society and provide the basis for most life on earth by generating oxygen as a product of photosynthesis. Fungi not only mediate critical biological and ecological processes including the breakdown of organic matter and recycling of nutrients, but they also play important roles in mutualistic associations with plants and animals. Members of the Kingdom Fungi also produce commercially valuable substances including antibiotics and ethanol, while other fungi are pathogenic and cause damage to crops and forest trees. Because fungi and plants play such fundamental roles in our lives, it is important to have a comprehensive knowledge of the taxa comprising these groups. However, at a time when we are increasingly recognizing the importance of these groups, we are impoverishing our biological heritage. Rates of species loss are reaching alarming levels as ecosystems are degraded and habitat is lost. This erosion of biological diversity threatens the maintenance of long-term sustainable development and protection of the earth's biosphere. |
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| Questions involving biological diversity are now of major concern to scientists, the general public, and government agencies with mandates for natural resource protection. Much of this concern has been directed toward tropical forest systems because of their high levels of biodiversity, although other regions, including the United States, deserve our immediate attention. Certainly, a first step toward conserving biological diversity must be based on a firm knowledge of the numbers and distribution of existing species. Developing good estimates of species diversity is also important in describing historical and current trends of species dynamics. Unfortunately, despite the existence of various state and regional surveys, the efforts of taxonomists and natural historians, and the publication of various floras, we still do not have precise estimates of the status of plant and fungal taxa in the United States. Estimates for vascular plant taxa in the United States range upward from 17,000 species (Morin, Morse et al., this section). In contrast to this well-studied group, only 5%-10% of an estimated 1.5 million fungal species have been described worldwide (Rossman, this section). |
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| Even though the bulk of information about our native vascular flora was collected in the 19th and early 20th centuries, significant data about the status of plants in the United States continue to be collected as species expand their ranges, as other species thought locally extirpated are rediscovered, as poorly surveyed areas are explored, and as species become extinct. Even in states like New York, which has a long and currently active program of botanical exploration, additional species of vascular plants continue to be documented as poorly surveyed areas are given more comprehensive coverage (Miller and Mitchell, this section). |
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| Herbaria and museums continue to be important repositories for this information because collecting by their personnel represents a significant effort at inventorying plant and fungal species in this country (Morin, this section). Unfortunately, their role is increasingly at risk as support for collecting declines. In other cases, a shortage of trained specialists will prevent an adequate inventory of biotic diversity. Although many regional checklists exist as well as excellent manuals that cover bryophyte systematics, floristic inventories of bryophytes have been hampered primarily by a lack of trained professionals (Merrill, this section). |
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| The flora of the American countryside has been much changed since European settlement. Over the past 20 years alone, more than 200 species of non-native vascular plants have been recorded in New York state; these species represent an important risk to native plant communities (Miller and Mitchell, this section). Human activities are responsible for the introduction of these invasive exotics as well as the extinction of some species with small geographic ranges or those restricted to unique habitats. |
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| If current trends in land-use continue, however, even species with more widespread distributions will be at risk. For example, lichens as a group are declining in many areas from the effects of air pollution. It is estimated that as much as 80%-90% of the original lichen flora has disappeared from urbanized areas (Bennett, this section). Likewise, marked declines in macrofungi have been documented in Europe although similar trends in this country have not been published because, in part, of the incomplete inventory and lack of monitoring of these groups in the United States (Mueller, this section). Among the more completely documented vascular plants, The Nature Conservancy reports that 9.8% of native species have been lost from at least one state, more than 200 native species have become extinct in the United States, and an additional 403 native plant taxa need protection under the United States Endangered Species Act (Morse et al., this section). |
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| The articles in this section represent an important step in describing the status of the plant and fungal taxa in this country. They provide a snapshot illustrating our knowledge of past and current distributions of plants; the importance of developing a more comprehensive data base for various groups, especially the fungi; and the need to develop a comprehensive inventory of the continually changing and evolving flora of the United States. If we are to understand the causes underlying the changes in patterns of diversity and make predictions about the threats of anthropogenic (human-caused) activities, we must have a quantitative understanding about the nature and distribution of the taxa composing our flora. |
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