7944

• UCREFRP Catalog Number: 7944
• Author: Hoar, A. R. and M. J. Erwin.
• Title: Relationships Between The Expansion Of Agriculture And The Reduction Of Natural Riparian Habitat In The Missouri River Floodplain Of Northeast Montana, From 1938 To 1982, ‎(paper-North American Symposium on Riparian Ecosystems and Their Management)‎.
• USFW Year: 1985.
• USFW - Doc Type: April 16-18, 1985.
• Copyright Material: NO

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Table 3.--Estimated loss (or gain) of riparian cover types
attributable to categories o change over time.
Rip arian Cover Tv pes
Categories of change Deciduous Scrub
fQr each time period Woodland Scrub Herbaceou,~ Totals
acres/year
Loss to development
1938 through 195fi 106 248 2123 2477
.1956 through 1974 167 234 904 1305
1974 through 1982 455 218 1519 2192
Loss to the River
1938 through 1956 52 109 237 398
196fi through 1974 26 40 28 94
1974 through 1982 96 159 118 373
Loss (gain) to other causes
1938 through 1966 ( 688) ( 9Z) 388 ( 392)
1966 through 1974
1974 t~(,8~ah 1982 ( 673)
X185 140
( 381 ( 612)
( 28161 (1145)
(1669 )
way. Since fsr more acres were converted to agri-
culture than all other developed types combined,
the "lose to development" ce~tegory, can be for the
most part, be thought of am a "loss to agricul-
ture" trtegory.
"Lone to development" accounted for a large
percentage (49 percent.) of the total riparian
losses during the entire period studied. Some of
each riparian type was developed during every
period, but substantially more of the herbaceous
type was lost to development then any other type.
Development accounted for 65, 64, and 79 percent
(chronologically) of all herbaceous losses. The
rate at which each riparian type was lost to
development changed over time. The rate of loss
declined for both the herbaceous and shrub-scrub
types, while it increased for tht forest type. It
appears that ss the amount of herbaceous and shrub
area declined, more emphasis may have been placed
on converting woodlands to agriculture.
"Loss to the river" included the loss of
riparian cover from-the shores of islands as well
as the mainland, due to bank erosion by water. It
also included loss of riparian cover from an area
downstream from Fort Peck psm, where earth was
removed and used to construct the Dam. Since then
this excavated area has filled with water. Floods
occurred during the study period that influenced
the, amount of riparian cover lost to the river. A
total of 12,238 acres of riparian cover was lost
to the river during the study period. This type
of loss accounted for only seven percent of the
total riparian losses during the entire period.
Less of each cover type was-lost to the river than
was lost to any other category during the same
period.
"Loss (or gain) to other causes" accounted
for all other effects of reduction and growth of
riparian vegetation caused by humans and nature
that resulted in the conversion of one type into
another. Again occurred whenever developed land
reverted to riparian cover (28,932 acres in
total), and when new riparian growth occurred on
soil deposited by the river (not specifically
calculated). The rate of change was quite
volatile with each cover- type undergoing periods
of loss and gain. Only three periods of loss
occurred and they were staggered, one in each time
period. The increase in forest loss attributable
to this category was acute between 1974 and 1982,
when a rate of gain of 673 acres per year dropped
to a loss of 1186 acres per year.
CONCLUSIONS
There is much concern over the loss of ripar-
ian habitat, especially in the western United
State, because of the importance of this habitat
to fish and wildlife resources. Although studies
conducted elsewhere have documented the loss of
this habitat, information was not available on the
status of riparian habitat on the Missouri River
in Montana. This fact plus the observations of
numerous biologists that rather large blocks (20
to 80 acres) of trees were being cleared in the
mid-to-late 1970's along the reach of Missouri
River reported upon here, with unknown habitat
consequences, led to this study.
A cursory examination of data in Table 2 may
lead one to believe, at least 1n the case of
forests, that there is not much reason for concern
about loss of this type in the study reach. There
was attually more of-the forest type in 1982
(23,189 acres) than there was in 1938 (18,374
acres). However, closer examination shows that
there was an increase of forests from 1936 through
1974, followed by a substantial loss between 1974
:and 1982. The data reflect a gain of (}~ percent
in this type in the 36-year interval between 1938
`and 1974, followed by a 37 percent loss in dust
-eight years between 1974 and 1982. Further confir-
mation of this reversal is shown in Table 3. The
annual rate of "gain due to other causes" of the
woodland type declined Prom about 680 acres per
year between 1938 and 1974 to a loss of 1185 acres
par year between 1974 and 1982. If the rate of
loss observed between 1974 and 1982 continues into
the future, there is valid reason to be concerned
about the longevity of the cottonwood forests in
thts reach of river.