MAPS & GRAPHS
Throughout this section of the Grizzly Times we display graphs and diagrams showing the data games being played by government officials to overstate increases in the Yellowstone grizzly bear population so as to, in turn, justify delisting.
It is important to remember that these games are being played at taxpayer expense and have real, life and death consequences for threatened grizzly bears. These graphs are based on data of the Interagency Grizzly Bear Study Team - the government's own 'scientific' mouthpiece.
Throughout this section, "the rest of the story", is shown to you - that is, the information NOT being told by the government agencies who are desperate for delisting to happen now.
The quartet of maps shown here are a timeline of grizzly bear extirpations in the contiguous U.S. between 1800 and 1970. Dark green identifies the range occupied by grizzly bears at each time step. Areas tinted yellowish green represent areas where grizzly bears were cumulatively extirpated during this 170-year period. Habitat occupied by grizzly bears has increased very little since 1970, just prior to when grizzly bears were listed under the ESA. See NCDE and GYE maps for more detail on recent changes in grizzly bear distributions. Maps by David Mattson.
Grizzly Bear Range Collapse 1800-1970
Current & Potential Grizzly Bear Habitat
This map compiles the results of analyses of potential grizzly bear habitat in the western U.S. Each analysis is identified by a different color and attributed to the researchers who produced them in the legend. Areas of potential but currently unoccupied habitat, primarily south of Yellowstone and the Northern Continental Divide, need further more detailed assessments of potential to support grizzly bears as part of range-wide recovery efforts.
Map courtesy of Center for Biological Diversity.
Yellowstone Grizzly Bear Distribution 1970s-2010
This map shows the distribution of the Greater Yellowstone Ecosystem grizzly bear population at different time intervals. Different shades of green represent distributions during successive decades, starting with the 1970s up until around 2000.
Orange denotes the change in distribution between the early 2000s and 2010. Red denotes areas of loss between 2010 and earlier time periods. Large increases in distribution occurred after the fires of 1988 and during a period when grizzlies were discovering and increasingly using moth sites on the east side of the ecosystem. The second period of increase occurred during a time of no population growth, but coincident with losses of whitebark pine, cutthroat trout, and elk.
Map by David Mattson based on published estimates of population distribution.
Northern Continental Divide Grizzly Bear Distribution 1980s-2012
This maps shows distribution of the Northern Continental Divide grizzly bear population at different time intervals. The lightest green corresponds to the 1980s distribution, intermediate green to the late 1990s distribution, and darkest green to the 2012 distribution. Orange or dark brown correspond with areas where the core distribution of the population contracted. Green dots denote recent peripheral sightings of grizzlies, suggestive of active colonization. The largest increase in distribution occurred between 2006 and 2012. Berry production was probably lower during this period compared to the 1990s. We also have no reliable indication of sustained population growth. Mortality has steadily and rapidly increased in this ecosystem beginning in the early 1990s, with the exception of a brief period during 2004-2009 which coincided with collection of the data that were used for the only the most optimistic published estimate of population growth.
Fragmentation & Location of Grizzly Bear Populations
The yellow dashed lines in this map identify fracture zones among populations or subpopulations of grizzly bears in the U.S. and southern Canada as of 2012. The numbers within each isolate are estimated population sizes. Note the small size and high degree of fragmentation among populations in northwest Montana, northern Idaho and adjacent areas of British Columbia. These populations are teetering on the brink of extinction. The yellow dotted line delineates extensive suitable but currently unoccupied habitat in the Selway-Bitterroot ecosystem of central Idaho.
From: Proctor, M.F., Paetkau, D...Strobeck, C. (2012). Population fragmentation and inter-ecosystem movements of grizzly bears in western Canada and the northern United States. Wildlife Monographs, 180, 1-46.
Heart of the Grizzly Bear Nation
This map shows how grizzly bear recovery can be achieved, by connecting grizzly bears in the lower 48 states to more robust populations in Canada. The biggest population in the lower 48 is centered around Glacier/Waterton Parks (red). Bears around Glacier can be reconnected to the Selway Bitterroot ecosystem in Central Idaho (brown), where grizzlies have been extirpated but where suitable habitat remains. Red arrows show the best prospects for connecting these populations. Dark pink shows core grizzly habitat in Canada and Yellowstone. The pale pink shows peripheral grizzly bear habitat.
Map by David Mattson based on published information on distributions, fragmentation, and potential habitat
Yellowstone Population Trend 1959-2016
This figure shows all estimates of size made for Yellowstone's grizzly bear population, 1959-2016. This period spans the ground-breaking study by Frank & John Craighead as well as the tenure of the Interagency Grizzly Bear Study Team. Briefly, the gray dots represent estimates of minimum population size, which is essentially a rock-bottom estimate of numbers of bears in the population. The dark burgundy dots or lines denote estimates of total population size, with the light burgundy vertical line or band around each estimate the extent of uncertainty. Estimates of population size since 2006 have been based on the so-called Chao2 adjustment, using two different estimated ratios of independent males to independent females in the population, which explains the higher and lower burgundy trend lines during recent times. The gray diamonds and standard errors for 1959-1980 are the results of a population simulation by Larry Roop for the period spanning closure of dumps in Yellowstone and listing of the population in 1975.
The take-away points from this graph are: (1) using comparable estimates of total size, the population has probably doubled since listing; (2) contrary to claims made by agency spokespeople comparing minimum population estimates from 1975 to total population estimates recently, the population did not quintuple in size; and (3) agency spokespeople have been distorting information on long-term population trend by comparing figurative apples with figurative oranges.
Yellowstone Population trend 2004-2016
Population trend 2014-2016
These graphs contain the same information as the figure immediately above, but differ by focusing on more recent periods of time. The figure at left shows trend between 2004-2016 based on four different--largely incommensurate--methods. I explained three of the methods above. The fourth, mark-resight, consistently produces a higher population estimate, but with much greater uncertainty, as denoted by the relatively large uncertainty intervals. The basic point, though, is that all methods are consistent in showing little or no increase for the Yellowstone grizzly bear population during this span of time. The graph above right focuses on the three most recent years, including 2015 and 2016, during which we saw record grizzly bear mortality. The population almost certainly declined during the last three years leading up to the 2017 removal of Endangered Species Act protection for Yellowstone's grizzly bears.
Yellowstone Grizzly Bear Mortality 1988-2016
Trends in Mortality from Conflicts with Hunters & Livestock Producers
These graphs show trends in mortality for Yellowstone's grizzly bear population, which are integral to understanding trends in total population size shown above. The graph at left shows total mortality by year as a 3-year running average (technically, "known and probable" deaths), relative to the period when greatest losses of whitebark pine were occurring (in yellow). Total mortalities skyrocketed during and after losses of whitebark pine and have remained high at the same time that population growth stalled, and then turned negative. Part of the point here is that dramatic increases in total mortality cannot be explained simply as a consequence of having more bears--which we don't have. In fact, reductions in population growth, recently into negative territory, are a logically consequence of many more bears dying.
The two graphs at right show two causes of death that have largely caused the dramatic upturn in total mortality: conflicts with big-game hunters, primarily during fall; and conflicts with ranchers over depredations on livestock. The hunter-related graph shows a dramatic upturn in bear deaths from this cause beginning around 2009 (red dots), coincident with sustained declines in numbers of hunters afield (gray dots). In other words, increasing deaths caused by hunters cannot be attributed to more hunters in the woods. Similarly, the bottom graph at right shows a dramatic upturn in numbers of livestock-related conflicts (pink dots) along with livestock-related bear deaths (red dots) also beginning around 2009. The black dashed line in each of the graphs at right is an estimate of ecosystem-wide availability of whitebark pine cones/seeds, which exhibited a sustained downturn beginning around 2007.
Northern Continental Divide Grizzly Bear Mortality 1988-2016
The graph at left shows trends in grizzly bear mortality for the Northern Continental Divide Ecosystem from 1969-2015. As with the graph above for Yellowstone, trend is shown as a 3-year moving average. Several important natural and policy-related events are noted, including the institution of Endangered Species Act protections in 1975, the cessation of sport hunting of grizzlies (yes, believe it or not, Montana continued to sport hunt grizzlies even after listing), and a berry famine that lasted from roughly 1998-2008. Berries are the most important source of energy and nutrients for bears in most of this ecosystem, especially west of the Continental Divide.
Some noteworthy patterns include a sustained drop in mortality after listing under the ESA, a jump in mortalities roughly 1/2-way through the berry famine, a subsequent drop, and then another jump beginning roughly 2011. None of this correlates very well with changes in population size.
In fact, as in Yellowstone, the large increases in numbers of bears dying from roughly 2004 on can't be explained by relatively modest increases in population size. More likely increases are explained by lack of food during the berry famine, and an expansion of bears into areas of human occupancy at a rate that far exceeds any population increase.