over under sideways down*: inertia of a transforming food ... · over under sideways down*: inertia...
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Over Under Sideways Down*: Inertia of a Transforming Food Weband Extinction Debt for Delta Smelt
* The Yardbirds, 1966
Bill Bennett Center for Watershed Sciences
Bodega Marine LaboratoryUC-Davis
Food Web & Extinction?
Alien food web rapidly transforming nativefood web.
A little Theory…Habitat loss, Hysteresis, and Extinction Debt
Evidence?
Is Extinction Inevitable?
Exotic SAV
Native SAV
Courtesy: Erin Hester,CSTARS, S. Ustin, UCD
Can “Flow” Alone Reverse the Regime?
Hysteresis – Muchharder to push system back!
Distribution of SAV June 2008
Boat samples withGPS referencing.
Exotic SAV primarily Brazilian waterweed.
1980 1990 2000 2010
0.0
0.1
0.2
0.3
0.4
0.5
0.6
De
lta
sm
elt
(g
m-3)
Delta smelt
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Largemouth bass
Bluegill sunfish
Redear sunfish
Ce
ntr
arc
hid
sp
p.
(g m
-3)
Inertia of Food Web Transformation
Egeria expansion:(Graph, S. Ustin 2016)
Centrarchid expansion:(Data, USFWS Beach seines)
Alien fishes: range expansion lags Egeria by
~ 10yrs.
Historical Habitat Use
4,615
55%
1,570
19%
585
7%
409
5%
399
4.8%
324
4%
135
1.6%
0
0
00
0
Erkkila et al.1948-49
7
0.08%
26
0.30%
1
0.01%
135
1.6%
5
0.06%
0.64%
Historical Habitat Use
MacCall’s (1990) Basin Model: Sardines -Individuals fill-up habitat of highest quality 1st, and then spill-over.
Errikla, 1940s
Hab
itat
Qu
ali
ty
Habitat Landscape
Depth indicates
optimal habitat.
Historical Habitat Use
MacCall’s (1990) Basin Model:
Mid-water Trawl > 2002
Hab
itat
Qu
ali
ty
Habitat Landscape
Historical Habitat Use
MacCall’s (1990) Basin Model:
Current
Hab
itat
Qu
ali
ty
Habitat LandscapeSuisun Bay
& Marsh
Cache Sl. &
Ship-channel
“The Alamo”
Sacramento R.
“ The Arc”
San Joaquin R.
& South Delta
Food Web & Extinction?
Habitat loss most important cause of extinction.
Most apparent for small-bodies species facedwith fragmented habitat.
Extinction Debt. Habitat has declined fasterthan ability to adapt. “You’re dead, but you don’t know that!” An extension of metapopulationtheory (Levins 1970, Tilman 1994).
Extinction Debt ?
Dynamic Regime Shift
Hysteresisreflects
Extinction Debt
-3 -2 -1 0 1 2-1
0
1
2
3
4
576
77
78
79
80
81
82
83
848586
8788 89909192 9394
95 969798 990001 02 0304 05060708 09
10 1112
131415
De
lta
sm
elt
(m
-3)
Water exports (m-3 sec)
0 5 10 15
0.0
0.2
0.4
0.6
Aut
ocor
rela
tion
lag
1
Years
P = 0.002, R2
= 0.53
System Behavior Indicates Regime Shift
Evidence for system dynamics slowing-downin years < 2001.
Points = autocorrelationcoefficients at lag 1, foryears before 2001.
Method: Dakos et al. 2008Proc. Nat. Acad. Sci.
Delta smelt biomass
Is Extinction Inevitable?
a. Delta region has fundamentally changed – since about 2000, it has undergoing a rapid transition to a new dynamic regime characterized by an alien food web.
b. Delta smelt disappearing, but historic optimal habitat hasn’t changed much; i.e., densities way down but optimal habitats still have highest densities.
c. Hysteresis associated with regime shift also reflects Extinction Debt.
d. Extinction is inevitable -UNLESS fundamental change occurs to halt the inertia of the alien food web.