De Jager Nathan R, Rohweder Jason J
U.S. Geological Survey Upper Midwest Environmental Sciences Center, La Crosse, WI, 54603, United States.
Environ Monit Assess. 2025 Jul 2;197(8):842. doi: 10.1007/s10661-025-14185-1.
We examined 30-year trends in the abundance and distribution of aquatic and floodplain vegetation, as well as human land uses in five study reaches of the Upper Mississippi River and one reach of the Illinois River using aerial photography collected in years 1989, 2000, 2010, and 2020. Permanently inundated area increased in all study reaches over the 30-year period. Increases ranged from 0.8% of study reach area in Pool 8 (73 ha) to as much as 6.5% of study reach area in Pool 13 (1,562 ha). Agricultural land use declined in the three study reaches where it was common (>35% of reach area). Agricultural declines ranged from 5.8% of reach area in Pool 26 (2,096 ha) to as much as 15.4% of reach area in the Open River reach (7,121 ha) and corresponded with a similar magnitude increase in permanently inundated area and semi-permanently inundated marsh classes. Total forest area declined in the four northern study reaches of the Upper Mississippi River. Forest loss estimates were on the order of 3.7% of study reach area in Pool 13 (905 ha), 2.1% of Pool 8 (364 ha), and 2.3% of Pool 4 (563 ha). Such losses represent 16.2%, 13.2%, and 10.9% of the total forest area in 1989 in Pools 13, 8 and 4, respectively. Permanently inundated area, wet meadow, shallow marsh vegetation, and mud were the main cover types that replaced forest cover in these reaches. In contrast to the decline in forest cover in the northern reaches, forest cover remained unchanged in the La Grange reach of the Illinois River and increased by 3.5% of study reach area (1,607 ha) in the southern Open River reach of the Mississippi River, mainly in former marsh vegetation and agricultural areas that were acquired by Federal and State agencies. The predominant changes observed across the study system (replacement of agriculture and forest area by permanently inundated area and semi-permanently inundated marsh classes) indicates that hydrological changes have been the main driver of change since 1989 throughout most of the Upper Mississippi and Illinois Rivers. Our study provides an example of changes in a regulated river system driven by regional-scale hydrological changes and local scale restoration actions, changes that could be compared against changes occurring in other large, regulated rivers across the globe.
我们利用1989年、2000年、2010年和2020年收集的航空摄影，研究了密西西比河上游五个研究河段和伊利诺伊河一个河段的水生及洪泛区植被丰度和分布以及人类土地利用的30年趋势。在30年期间，所有研究河段的永久淹没面积均有所增加。增加幅度从第8号河湾（73公顷）占研究河段面积的0.8%到第13号河湾（1562公顷）占研究河段面积的6.5%不等。在农业用地常见的三个研究河段（占河段面积>35%），农业用地有所减少。农业用地减少幅度从第26号河湾（2096公顷）占河段面积的%到开阔河段（7121公顷）占河段面积的15.4%不等，且与永久淹没面积和半永久淹没沼泽类别类似幅度的增加相对应。密西西比河上游北部的四个研究河段的森林总面积有所减少。森林损失估计约为第13号河湾（905公顷）占研究河段面积的3.7%、第8号河湾（364公顷）占2.1%、第4号河湾（ 563公顷）占2.3%。这些损失分别占1989年第13号、第8号和第4号河湾森林总面积的16.2%、13.2%和10.9%。永久淹没面积、湿草甸、浅沼泽植被和泥地是这些河段取代森林覆盖的主要覆盖类型。与北部河段森林覆盖减少形成对比的是，伊利诺伊河拉格兰奇河段的森林覆盖保持不变，密西西比河下游开阔河段的森林覆盖增加了占研究河段面积3.5%（1607公顷），主要增加在联邦和州机构收购的原沼泽植被和农业区域。整个研究系统观察到的主要变化（农业和森林面积被永久淹没面积和半永久淹没沼泽类别取代）表明，自1989年以来，水文变化一直是密西西比河上游和伊利诺伊河大部分地区变化的主要驱动因素。我们的研究提供了一个由区域尺度水文变化和局部尺度恢复行动驱动的调节河流系统变化的例子，这些变化可与全球其他大型调节河流发生的变化进行比较。
