In order to quantify the movement of nutrients into and out of Otsego Lake, and to attain a be tter understanding of the relationship between the lake and its watershed, a two year comprehensive, precipitation-based nutrient study was conducted (Albright, 1996). From January, 1991 through April, 1993 all major streams tributary to Otsego Lake were investigated, and all significant runoff events were monitored.
Throughout the first study year (Jan. 1, 1991 - Dec. 31, 1991), nine tributaries considered to be the most significant in the watershed with respect to the sizes of their drain age basins (Figure 5) were selected for monitoring on a precipitation event basis. The Susquehanna River, the sole outflow from the lake, was also monitored. Descriptions and locations of the ten sites are summarized in Table 5c. Baseline hydrologic monitoring was accomplished by daily staff gauge observations for which site-specific, stage-discharge relationships had been previously determined (Table 5d). Baseline monitoring included the analyses of temperature, dissolved oxygen, and pH using a H ydrolab Surveyor II multiparameter water quality monitoring instrument which was calibrated immediately prior to use (Hydrolab Corporation,, 1984). Water samples were collected biweekly and were analyzed for total phosphorus (as P) (persulfate digestion followed by automated stannous chloride method), nitrite+nitrate (as N) (cadmium reduction), and chlorides (mercuric nitrate titration). Samples were also analyzed for specific conductance (Beckman conductivity bridge, Model RC-16C), alkalinity (tit ration to pH=4.6 with 0.02 N H2SO4), and turbidity (Monitex Model 21PE portable nephelometer). Additional discharge observations and water samples (taken concurrently) were collected at a greater frequency during periods of elevated runoff. While no predetermined sampling schedule was followed, the intensity of data collection was dependent upon the extent and intensity of rainfall, the extent of associated snowmelt, and the period since the antecedent event.
Tables 6a and 6b indicate levels of dissolved oxygen, alkalinity, conductivity, pH, and chlorides in several major streams around the lake observed sporadically between 1970 - 1975 (Harman et al., 1980), and in 1991, respectively. Some of the variations between these data sets may be due to the seasonality of data collection.
USEPA funding provided for the establishment of several automated discharge monitoring and water sampling stations around the lake for use during the second study year (M ay 1, 1992 - April 30, 1993). This allowed for the collection and synthesis of a more comprehensive data set. Throughout this phase of the study, three tributaries whose drainage basins were considered to be the most significant and/or representative in the watershed, in terms of land form and land use practices, underwent constant stage monitoring. The Susquehanna River was also monitored. As changes associated with both discharge and chemical characteristics in the river tend to be gradual [as i s typical of lake outflows (Cooke et al., 1993)], manual discharge data and sample collections were considered adequate for the determination of its export values. Baseline monitoring was consistent with the previously outlined protocol, except for the omission of the analyses of alkalinity and turbidity. Throughout this interval total phosphorus was analyzed using single reagent ascorbic acid colorimetric procedure following persulfate digestion. Event monitoring was accomplished using Sigm a Streamline 800SL automated samplers equipped with integral flowmeters; predetermined sampling regimes were initiated upon a rise in stream level and continued throughout the duration of the event. Samples collected in conjunction with events were analyzed for total phosphorus, chlorides, and suspended sediment (Figure 6a-d).
Quality assurance/quality control was in accordance with the New York State Department of Health. Internal control consisted, in part, of duplicate analyses, reference samples, and spike recovery (NYSDOH, 1992). External control was administered by the NYSDOH and consisted of performance evaluation samples and performance audits.
Among the ten sites monitored throughout the first year, 1,619 discrete samples were collected, covering both baseline conditions and 29 runoff events. Throughout the second year, 1,289 discrete samples and 60 flow-weighted composite samples were collected among the four sites and were used to describe both baseline conditions and 44 runoff events.
Paired discharge and concentration data were tabulated for each monitored tributary. Where unavailable, concentration values were estimated by interpolating between the observed values; baseline characteristics were assumed until the onset of event conditions. Hydrologic loading was calculated as the integration of the plot of discharge vs. time. Similarly, chemical loadings were calculated as the integration of the plot of the product of discharge and chemical concen tration vs. time.
Loadings contributed by unmonitored portions of the watershed, including the basins of several small, intermittent streams as well as the downstream unmonitored portion of monitored tributaries, were estimated by applying export rates of monitored tributaries having similar land form and land use characteristics (Walker, 1986; Richards, 1989; Cooke et al., 1993). These areas together comprise 14.7% of the watershed. Estimates had to be made of loadings by those tribu taries which had been monitored throughout the first year, but not the second. This was done by utilizing relationships recognized between these tributaries and those which had been monitored for both years. Export values for each parameter of interest by each monitored tributary measured in 1991 were used to generate export ratios between streams monitored for the first year only and the most similar stream which had been monitored for both years. Second year export rates were then estimated as the product of these ratios and the measured rates observed on monitored tributaries during the second study year.
Non-fluvial components of the hydrologic and nutrient budgets including direct precipitation, atmospheric deposition, lake level changes, potable water withdrawal, evaporation, and contributions by lakeside septic systems were also considered. Lake level readings and total phosphorus contributed by atmospheric fallout were monitored at the Biological Field Station. Precipitation data were collected at the Village of Cooperstown (Hollis, 1994) as was potable water withdrawal (Linn, 1994). Evaporation rates were estimated using Class A evaporation pan data collected in Ithaca, NY (Eggleston, 1994); this site experiences similar patterns of cloud cover and solar radiation to the study area. A coefficient of 0.7 was applied to the pan data to estimate lake evaporation (Jones, 1992; Cooke et al., 1993). Total phosphorus contributed by lakeside septic systems was estimat ed by determining the number of public and private non-sewered dwellings within 300 meters of the lake. Phosphorus content in domestic waste water was estimated to be 0.8 kg/capita/year (Dillon and Rigler, 1975). Even under ideal conditions, plumes of groundwater having greatly elevated phosphorus levels have been documented down gradient from tile beds (Schiff et al., 1995; Ptacek and Crowe, 1995). The severity of the limitations of local soils to septic tank absorption fields (Department o f Geology, 1994) leads to high rates of migration. Given present setbacks and average age of lakeside septic systems, it is assumed that current phosphorus loading to the lake equals that introduced into these systems annually. The average occupancy in the towns surrounding the lake is 2.74 persons per household (Carlton, 1994). Contributions by residential dwellings (RD) was determined as:
RD=(permanent dwellings x 2.74 x 0.8 kg phosphorus) +
(seasonal dwellings x 2.74 x 0.33 year x 0.8 kg phosphorus).
Similarly, values were estimated for contributions by lakeside commercial establishments by determining numbers of employees on a time-weighted basis (ie. seasonality and hourly status were considered). Telephone surveys were used to estimate the annual number of visitors to such establishments. While potential phosphorus loadings by this group are given for comparative reasons, these values were omitted from the final phosphorus budget summary, as no valid standards were found to account for their contributions. Septic contributions are summarized in Table 7. A summary of the hydrologic budget is given in Table 8. While groundwater movement to and/or from the lake undoubtedly exists, the closeness of the measured water inputs to outputs would indicate that groundwater movement is either negligible or balanced.
Runoff and export rates by each drainage basin are summarized in Table 9 (refer to Table 5 for corresponding land use characteristics) . The annual loadings of these parameters by each tributary are presented in Table 10; a summary of all components of the chemical budgets is given in Table 11.
Various forms of phosphorus are available for algal uptake to varying degrees (Albright, 1996). Soluble inorganic phosphorus is generally considered immediately available, as is much of the dissolved organic fraction (Brown et al., undated). Bioavailability of particulate phosphorus is more variable. Bouldin et al. (1 975) reported that only about 4% of this fraction delivered to Cayuga Lake by Fall Brook was available (Reckhow and Chapra, 1983). Brown et al. (undated) indicate that 20%-40% of sediment phosphorus from agricultural watersheds is bioavailable, while Grobler and Silberbauer (1985) reported that 40%-100% of this fraction was available in South African river basins. Due to the interconvertibility of the various fractions, any form of phosphorus can be considered potentially available in the long term, though only between 50% and 60% of total phosphorus is generally regarded as such (Sonzogni et al., 1980).
Tributaries located in the northern portion of the watershed (Cripple Creek, Hayden Creek, and Shadow Brook) possess the most extensive catchment areas, together comprising 29,662 acres, or 64% of the watershed, and are the largest contributors to the hydrologic and nutrient budgets. Therefore, they are the most important with regard to the effects on water quality of the lake. Relatively high export rates were observed for total phosphorus, suspended sediments, and, most notably, nitrite+nitrate (NO2+NO3); collectively, these tributaries were responsible for 74%, 81% and 86% of the fluvial loadings of these materials, respectively. Alkalinity levels in these streams tend to be quite high, with the averages ranging between 165-190 mg/l as CaCO3, as limestone bedrock predominates. It should be noted that Clarke Pond, an impoundment of approximately 12 acres near the lake on Cripple Creek, has seemed to effectively serve as a retention basin, allowing for the settling of much of the sediment and associated total phosphorus, and thus preventing its export to the lake.
Willow Brook is the only tributary draining an area having significant urban characteristics. Occupying less than 5% of its drainage basin, the Village of Cooperstown represents most of the urban land use area included and lies at the lower reaches of the stre am adjacent to the lake. Runoff characteristics observed were typical of an urban land use setting, including lower base flow, shorter response time, and higher peak discharge (Beaulac and Reckhow, 1982) (Figures 6a-d). The decreased permeability associated with urban land cover, coupled with a loss of vegetation, leads to increased exports of sediment and phosphorus, particularly in conjunction with storm events. Willow Brook was found to have greatly elevated exports of these parameters; total ph osphorus export was over five times as great, and suspended sediment ten times as great, as was observed in a relatively undisturbed adjacent basin of similar size and land form. Chloride export was five times higher than was seen in any other tributary. This is likely a result of the use of deicing salts throughout the winter, despite municipal efforts to reduce utilization. As Willow Brook drains a relatively small area (927 acres), its contribution to the overall nutrient budgets does not, at fi rst glance, seem to be excessive. However, perhaps of greater importance than the volumes of phosphorus and sediment delivered are the timing and location of delivery. The vast majority of the loadings by the three largest streams, mentioned above, are associated with spring runoff. During this time, low water temperatures in the lake preclude the uptake of phosphorus by algae. By the time temperatures have warmed to a point where algal growth is stimulated, much of the phosphorus, having been as sociated with particulate material, has settled out of the water column and is thus unavailable for algal use. Conversely, Willow Brook, because of its basin's urban characteristics, responds to storm conditions throughout the year. Shadow Brook, which was observed to be second only to Willow Brook in total phosphorus export rates, contributed 4.3% of its annual phosphorus load between June and September (i.e. the peak algal growing season). During this same period, Willow Brook delivered 11.8 % of its annual phosphorus load.
The above problem associated with Willow Brook is further aggravated by the location at which this stream enters the lake. Willow Brook empties into shallow water in close proximity to public waterfront and recreational boating facilities. The resulting levels of power-boat traffic lead to constant agitation (Yousef, 1978) of nutrient rich sediments supplied by Willow Brook (Albright, 1996). Recent research suggests that phosphorus sorbed to particulate materia l may be available for algal growth when suspended in the water column (Bostrom et al., 1982; Yousef et al., 1980; Premozzi and Provini, 1985). Local degradation of water quality near the mouth of Willow Brook, impairing recreational use, attests to that phenomenon. However, lakewide impacts are probably not extensive, as the total loading by this tributary is relatively small. Also, the soluble nutrients delivered by this stream likely have a short retention time due to the close proxim ity of its mouth to the Susquehanna River (Oglesby, 1996). Conversely, loading to the lake by the more extensive catchment areas in the northern portion of the watershed may have greater long-term, lakewide effects. Particulate phosphorus entering the north end of the lake and Hyde Bay is largely deposited in shallow water. Perturbation of these sediments and nutrient cycling by macrophytes, coupled with long rentention time because of the distance to the lake's outlet, may compound the effects of ph osphorus derived from these regions.
The remaining tributaries in the watershed seem to have moderate to good water quality, as seen by their respective nutrient export rates. Streams on the east side of the lake, located south of Shadow Brook, are all short tributaries with steep gradients. The source of water in these streams during the summer is primarily groundwater emanating from exposed shales and sandstones. They are low in dissolved solids and nutrients, particularly nitrates. Stre ams on the west shore pass through areas having variable intensities of agriculture and population distributions; nutrient levels are likewise variable.
The same nine tributaries to the lake were studied by Komorowski in 1992-3 (1994) to gain an understanding of their annual periphyton biomass and algal species composition. Flow-weighted average nutrient concentrations were derived from data collected by Albright (1996), above. The streams flowing through agricultural lands generally possess ed the highest yearly average of nutrient concentrations and algal biomass (Table 12). Their combined yearly averages of T-PO4 equaled 0.057 mg/l, NO2+NO3 equaled 1.08 mg/l, chlorophyll a equaled 0.691 mg/m2/d, and ash-free dry weight equaled 133.86 mg/m2/d. Streams with forested basins generally exhibited lower yearly averages of the above factors; T-PO4 = 0.037 mg/l, NO2+NO3 = 0.46 mg/l, chlorophyll a equaled 0.314 mg/m2/d, and ash-free dry weight = 58.47 mg/m2/d. The stream collecting urban runoff had high T-PO4 (0.334 mg/l), low NO2+NO3 (0.37 mg/l) and chlorophyll a (0.032 mg/m2/d). Ash-free dry weight = 16.28 mg/m2/d.
Temporal patterns were considered important factors affecting stream ecology throughout the year because the change of seasons (temperature, light, discharge) stimulates variations in nutrient concentrations and availability as well as directly affects periphyton biomass and diversity (Table 13). The highest seasonal averages of T-PO4 and NO2+NO3 in the agricultural streams occurred during the winter and in the forested streams in the summer. Algal biomass in the agricultural and forested streams was highest in the spring. At the same time, an increase in diversity in similar periphyton communities was observed (Table 13).
A study of the characteristics of Otsego Lake tributary streams utilizing macrobenthic indicators of stream quality was conducted during the summer of 1974 (Harman, 1975). Samples were collected using Hester-Dendy artificial substrate benthos samplers (Hester and Dendy, 1962) according to the prescribed methods (Beak et al., 1973). The organisms were determined to the most specific taxa possible (genus in most cases) and the ecological requirements typical of the common representatives of the genera presen t were considered important in the evaluation of the biotopes concerned. Table 14 indicates the genera represented in each habitat sampled.
A summary indicating the overall conditions in Cripple Creek, Shadow Brook, and Hayden Creek at that time follows. Details of the study can be found in Harman (1975). In Cripple Creek, the faunal zones remained the same in the three areas studied. The diversity gradually became lower as one moved downstream, apparently reflecting habitats slightly de graded from the input of nutrients from the headwaters to below Clarke Pond. The results obtained in Shadow Brook and Hayden Creek indicated a greater degradation due to enriched conditions. The diversity dropped from the headwaters to the intermediate stations, then increased dramatically in the downstream areas despite the loss of stenotopic species typical of oligotrophic waters. The increase was due to the addition of many lentic representatives possessing a competitive advantage on soft substra tes and tolerant of low oxygen typical of drowned stream mouths. Eutrophication was not so severe in either case so as to eliminate the vast assemblage of eurytopic organisms that occur in most aquatic biotopes, although high populations of oligochaetes in Shadow Brook indicated a severely stressed environment.
Qualitative collections of macrobenthos by Maxwell and Harman (both unpublished) associated with academic offerings at the BFS during the 1980s and 1990s indicate little change since t he 1974 studies on the above mentioned streams. Leatherstocking Creek possesses a more stenotopic fauna indicative of well oxygenated waters similar to the many small and often intermittent, shaded, hanging valley spring-brooks entering the lake along the east and west shorelines. Similarly, it has exhibited little in the way of macrobenthic faunal changes over the years despite documented warming trends affected by removal of streambank vegetation and associated siltation (Harman, Unpbl.; Hayes, 19 90; Brooking, 1992; Hakala, 1994).
The fish fauna of the Otsego Lake watershed
This contribution is derived in large part from Foster (1996a). Information from other sources is cited as presented. Early Biological Field Station fisheries surveys (New, 1971; 1973; Harman et al., 1980; MacWatters, 1980; 1983) focused on developing comprehensive listings of the fish fauna of Otsego Lake and its tributaries. Unfortunately, they did not separate stream fauna from lake fau na, nor did they describe the fish fauna of specific streams in the Otsego Lake watershed. In 1970 the New York State Department of Environmental Conservation (NYSDEC) conducted electrofishing surveys throughout the length of Hayden Creek and Shadow Brook (Sanford, 1993). A similar survey was conducted on the main stem of Lawyers Creek in 1985 (Schiavone, 1993). Biological Field Station surveys utilizing seines (150 foot haul seine and a 25 foot, fine mesh shore seine) and electrofishing (chain shocke r and Smith-Root backpack shocker) have been conducted on Leatherstocking Creek (Hayes, 1991; Brooking, 1992; Hakala, 1994), White Creek (Foster et al., 1996), Shadow Brook (Bassista and Foster, 1996), Hayden Creek (Heavey, 1996) and in Cripple Creek (Miner, In prep.). In 1989 a quantitative electrofishing survey was conducted on one site on the main stem of each permanent watershed stream (Hayes, 1990). Data from these 1989-96 surveys were pooled to provide an indication of species richness and are included with the earlier data in Table 15a. Specimens from these sites in the collections of the NYS Museum (NYSM) (Daniels, 1996) are also included.
Lotic fish habitat is defined here as those streams with sufficient flow to support year-round fish populations. In the watershed these habitats comprise 1st and 2nd order streams. The minimum lotic fish habitat is found in 1st order streams, the smallest unbranched tributaries that appear on a 1:24,000 quadrangle map (after Leopold et al., 1964). These first order streams include Willow Brook, Brookwood Creek, Three-Mile Point Stream, Mohican Canyon Creek, and Cripple Creek. Second order streams occur when two or more 1st order streams join. Second order streams in the watershed are Leatherstocking Creek entering the Lake along the west shore and White Creek, Hayden Creek and Shadow Brook at the north end.
Since 1988, 34 species of fish representing nine families have been captured in the streams feeding Otsego Lak e. The assemblages in these streams are dominated by minnows, which make up between 52% of the individuals collected in Shadow Brook (Basssita and Foster, 1966) and 100% in Willow Brook and the stream at Three-mile Point. Blacknose dace and creek chub are the most abundant. The central mud minnow (Umbra limi) was collected in Cripple Creek in 1996. It is the first record of this species in the Otsego Lake watershed (O'Conner, In prep.).
Only 12 of the above species (brown trout, bro ok trout, rainbow trout, redside dace, cutlips minnow, common shiner, northern redbelly dace, blacknose dace, longnose dace, creek chub, pearl dace and margined madtom) are primarily stream species (Smith, 1985; Scott and Crossman, 1973). The remaining species, found in the watershed streams have significantly larger populations in Otsego, or other watershed lakes.
While species richness in the Otsego Lake watershed is related to stream order, the concept does not fully describe the range ob served. Within the same watershed, stream order is usually correlated with stream size, stream length, discharge and drainage basin size (Harrel et al., 1967; Platts, 1979). Of these factors, stream length appears to be the most important locally. For example, Willow Brook and Three-Mile Point Creek have both the shortest length and the lowest species richness, while Shadow Brook and Hayden Creek have the longest unbroken length of fish habitat, and maintain the greatest number of fish species (Table 15a). Species richness is much higher below insurmountable barriers as demonstrated at most Route 80 road crossings. For example, in Leatherstocking Creek four species are found above the road crossing, while 19 species are found in a much smaller reach below this obstruction (Hakala, 1994). In Trout Brook, five species are found above the crossing, while 14 species are found below. Thus, access to streams from Otsego Lake has a tremendous impact on the fauna. The length of stream between the Lake and an insurmountable barrier also seems to be a major factor determining the number of species present.
The only fish considered to be widely distributed throughout the watershed are: Blacknose dace (9 streams), longnose dace (7), and creek chub (8). These were found in at least two-thirds of the streams sampled. Most species had very restricted distributions and occurred in one-third or less of the streams sampled. They were; rainbow trout (1), brook trout (3), alewife (2), redsi de dace (2), cutlips minnow (3), golden shiner (2), emerald shiner (2), common shiner (2), spottail shiner (2), northern redbelly dace (3), bluntnose minnow (3), fallfish (2), pearl dace (1), central mud minnow (1), chain pickerel (1), channel catfish (1), margined madtom (3), redbreast sunfish (3), black crappie (1), smallmouth bass (2) and yellow perch (3).
Of the numerous ways of subdividing fish habitat in streams (Hocutt & Wiley, 1986), the watershed fits best into three faunal zones ; headwater tributaries, intermediate pool-riffle segments, and still-water lowland segments. In the Otsego Lake watershed, headwater tributaries flow either directly into the lake (e.g. most streams along the east shore), or into a larger stream segment. These 1st order streams are characterized by swift, cold waters. Headwater tributaries occur in high-gradient regions of the watershed. Intermediate segments have a combination of pools and riffles, and merge imperceptibly above with the headwaters dominated by rocky riffles and below with the still-water depositional zones dominated by silty pools. Intermediate pool-riffle segments are characterized as having a moderate gradient and cool water. Still-water lowland segments occur primarily near the mouths of the largest streams (Cripple Creek, Hayden Brook, Shadow Brook and Leatherstocking Creek). They are characterized by having warm, turbid waters and represent reaches drowned by artifically raised Lake levels.
Most species (e.g. alew ives, chain pickerel, emerald shiner, spottail shiner) occurring near the mouths of streams are more typical of the Lake ecosystem rather than that of small streams. For example, centrachids represented by six species of sunfish and bass are typical of the littoral zone of Otsego lake, and compose as much as 35% of the total fish found at the mouth of Shadow Brook (Bassista and Foster, 1996). Lake species also tend to be concentrated near watershed lakes (Allen, Young, Weaver and Summit Lakes) and we tlands. The fish fauna of lower portions of Hayden Creek, Leatherstocking Creek and Shadow Brook, which have large still-water sections are dominated by lake species. Some of these are transient members of the fish fauna of streams occurring for limited periods. For example, rainbow smelt are found in stream mouths in the early spring.
The intermediate segments of streams contain the greatest numbers of species and the largest populations of fish. Pool-riffle segments are dominated by minnow s and suckers, with smaller numbers of madtom, darter and sunfish. As part of the Susquehanna River drainage, brook trout, blacknose dace and sculpin would be expected to dominate (Holcutt and Wiley 1986). However, sculpin are absent and trout seldom dominate.
There are only four streams in the watershed that presently have year-round trout populations: Leatherstocking Creek, Cripple Creek, Hayden Creek and Shadow Brook. Trout in these streams tend to occur in fragmented populations, partic ularly during the summer. Year-round brook trout waters can be found in Leatherstocking Creek around Keys Farm (Huff Road Crossing) and between Leatherstocking Falls and the mouth. Brown trout occur in Cripple Creek between Tiejin Road and Frank Patterson Road and in the Hayden Creek main stem from above the Route 53 crossing to Shipman Pond. The only brook trout in Hayden Creek appear at the first tributary crossing Route 80. In Shadow Brook, small numbers of brook trout, brown trout and rainbow trou t occur in fragmented populations in the lower portions of tributaries and the main stem from Briar Road to Route 20.
The lakes within the Otsego Lake watershed (Allen Lake, Moe Pond, Summit Lake, Weaver Lake and Young Lake) are all shallow and warm. The fish fauna is dominated by warm water species such as sunfish, bullhead, pickerel, carp and golden shiner (Table 15b). With the exception of Moe Pond, the fish fauna found in the watershed lakes is remarkably similar. Young Lake and Weaver L ake, which are both in the Cripple Creek drainage basin separated by 0.6 km of stream, have the highest number of species (8) in common. Black crappie, found in Young Lake and reported from Summit Lake, is the only species present in the watershed lakes that does not presently occur in Otsego Lake (McWatters, 1983).
In 1993 catch per unit effort for a 24 hour set using a 4-foot Pennsylvania trap net (50' lead) and a 300 foot trammel net (8' deep, 12" stretch outer mesh, 10" stretch inner mes h) provided a crude measure of relative abundance and species richness (Table 15c). Abundance of fish was greatest in Young Lake, followed by Weaver and Allen Lake, Summit Lake and Moe Pond. Golden shiner was the most abundant species in Young Lake and Allen Lake, brown bullhead in Moe Pond and Weaver lake, and white sucker in Summit Lake. Allen and Summit Lakes are the only two which contained largemouth bass, chain pickerel, and adult yellow perch. Young Lake seemed to have the highest density of pan fish, while Allen Lake had the highest density of game fish. Allen lake appeared to have the best balance in terms of predator-prey ratio. Lack of boat access there may result in a reduced catch of large piscivorous fish which would serve to maintain it. Poor predator-prey ratio in the other lakes may be the cause of overpopulation and stunting (Foster and Frost, 1996).