Determining Deer Population Objectives
DEC is responsible for managing New York's wild deer resource for the benefit of all citizens of the state, now and in the future. Understanding how citizens are benefiting from or being harmed by deer and what their values and priorities are with respect to deer management is an important part of fulfilling that responsibility. DEC must also manage deer in an ecologically responsible manner. Because heavy browsing (feeding) by deer can have profound and long-lasting negative impacts on forest ecosystems (PDF), keeping those impacts at a sustainable level is a top priority for DEC deer managers.
In 2020, DEC began using a two-part approach to establish deer population trajectories for each Wildlife Management Unit (WMU) Aggregate, incorporating data about public desires for deer population change and the status of deer impacts on forest sustainability. Outcomes of this process yield a recommendation to manage the deer population toward an approximate 25% increase, a 25% decrease, or for the local population to remain stable for the next 10-year period. We are now using a survey-based process to gather the information on citizens' preferences that will help DEC biologists set deer population objectives.
Public Preferences for Changes in Deer Abundance
In 2018-2020, DEC collaborated with the Cornell University Center for Conservation Social Science to survey homeowners throughout the state with questions about:
- their interests and concerns related to deer;
- how they would like to see the deer population in their area change over the next several years; and
- how important deer management issues are to them.
Deer Impacts to Forests
To assess forest sustainability across the landscape of New York, we assessed the level of regeneration debt existing in our forests. "Regeneration debt" describes a condition that predicts the eventual loss of canopy species due to limited abundance of seedlings and saplings or a mismatch in species composition relative to the forest canopy. Essentially, regeneration debt exists when the number of seedlings and saplings is inadequate to fully replace the mature trees or when the species of seedlings and saplings present suggests a broad transition in forest composition. When regeneration debt is absent, the forest is typically sustainable and capable of replacing itself. Forests with a low level of regeneration debt are vulnerable, compromised by inadequate seedling or sapling abundance or species mismatch. When regeneration debt is moderate to severe, the existing forest is unlikely to replace itself in the current form.
Regeneration debt may be influenced by a variety of factors (e.g., abiotic factors, invasive plant species, forest management practices), not just excessive deer browse. To parse out areas where deer impact is the primary contributing factor to poor regeneration, we used a model which predicts changes in seedling abundance following a potential reduction in deer abundance. In portions of New York, a modest reduction in deer abundance was predicted to yield either marginal change or a slight decrease in seedling abundance, suggesting deer impacts are not a substantial factor in forest regeneration in those areas. In other areas, seedling abundance was predicted to increase. Of primary concern for deer management are the areas where forest regeneration was vulnerable or not acceptable and models predicted a likely increase in seedling abundance if deer populations are reduced.
Deer Population Trend Objectives
DEC used both the public input and forest impact assessment to determine whether the deer population could increase, or should decrease or stay the same. A full description of this process and the decision
framework is in Appendix 2 of our New York State Deer Management Plan: 2021-2030.