The invasion of non-indigenous plants is considered a primary threat to integrity and function of ecosystems. However, there is little quantitative or experimental evidence for ecosystem impacts of invasive species. Justifications for control are often based on potential, but not presently realized, recognized or quantified, negative impacts. Should lack of scientific certainty about impacts of non-indigenous species result in postponing measures to prevent degradation?
Recently, management of purple loosestrife (Lythrum salicaria), has been criticized for lack of evidence demonstrating negative impacts of L. salicaria, and management using bio control for lack of evidence documenting the failure of conventional control methods. Although little quantitative evidence on negative impacts on native wetland biota and wetland function was available at the onset of the control program in 1985, recent work has demonstrated that the invasion of purple loosestrife into North American freshwater wetlands alters decomposition rates and nutrient cycling, leads to reductions in wetland plant diversity, reduces pollination and seed output of the native Lythrum alatum, and reduces habitat suitability for specialized wetland bird species such as black terns, least bitterns, pied-billed grebes, and marsh wrens. Conventional methods (physical, mechanical or chemical), have continuously failed to curb the spread of purple loosestrife or to provide satisfactory control.
Although a number of generalist insect and bird species utilize purple loosestrife, wetland habitat specialists are excluded by encroachment of L. salicaria. We conclude that negative ecosystem impacts of purple loosestrife in North America justify control of the species and that detrimental effect of purple loosestrife on wetland systems and biota and the potential benefits of control outweigh potential risks associated with the introduction of bio control agents. Long term experiments and monitoring programs that are in place will evaluate the impact of these insects on purple loosestrife, on wetland plant succession and other wetland biota.
外來植物的入侵被認為是對生態系統完整性和功能的主要威脅。然而，關於入侵物種對生態系統的影響，目前還缺乏定量或實驗證據。控制的理由往往是基於潛在的，但目前尚未實現，承認或量化的負面影響。缺乏對非本地物種影響的科學確定性是否會導致推遲採取措施防止退化?
近年來，紫松香的管理因缺乏證據證明紫松香的負面影響而受到批評，而使用生物控制的管理因缺乏證據證明傳統控制方法的失敗而受到批評。雖然在1985年控制項目開始時，幾乎沒有關於對原生溼地生物群落和溼地功能的負面影響的定量證據，最近的工作表明,紫珍珠菜的入侵北美淡水溼地改變分解率和養分循環,導致溼地植物多樣性的減少,降低了授粉和種子產量的原生千屈菜,並減少等專門的溼地鳥類棲息地適宜性黑燕鷗,鷺鷥,斑嘴巨鸊鷉,和沼澤鷦鷯。傳統的方法(物理的、機械的或化學的)，一直未能抑制紫色松香的蔓延或提供令人滿意的控制。
雖然有許多多科性昆蟲和鳥類利用紫斑潛蠅，但由於千屈菜的入侵，溼地生境專家被排除在外。我們的結論是，北美紫斑潛蠅對生態系統的負面影響證明了控制紫斑潛蠅是合理的，紫斑潛蠅對溼地系統和生物群落的有害影響以及控制紫斑潛蠅的潛在好處超過了引入生物控制劑的潛在風險。現有的長期實驗和監測項目將評估這些昆蟲對紫線蓮、溼地植物演替和其他溼地生物群落的影響。
decomposition detrimental compositionencroachment experimental curb
suitability theoretical accomplishment
devastating stop sustainability
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