The underlying philosophy of PHE is an integrated approach to meeting rural community needs for family planning, basic health, and natural resource management in a comprehensive and coordinated manner. Advocates believe the PHE approach is more effective than delivering these services in stand-alone or parallel programs. PHE projects play an important role in areas where demographic trends (such as natural population growth and human migration) place pressure on the environment; where degraded natural resources impact the health and livelihoods of local communities; and where a lack of health services, especially family planning and reproductive health impacts peoples health and well-being.

Biodiversity conservation is critical for sustainable development—as the natural biological underpinning that supports human life and well-being. Threats-based analyses can help determine the extent of pressures in a given biodiverse area and offer science-based strategies and approaches to address the root causes of these threats. USAID lists five primary direct threats to global biodiversity: conversion of natural habitat to croplands, urban areas or other human-dominated ecosystems; overexploitation of valuable species; introduction of invasive species; pollution of water, land and air; and macro-environmental change such as climate change, desertification and other environmental change originating from outside the natural habitat. In addition are human-induced threats such as natural population growth; human migration; unsustainable agricultural practices; inappropriate livelihood strategies and weak governance structures. The documents in this section provide more details on the biodiversity threats and environmental impacts.

One of the primary underlying questions for the PHE community is: “Do integrated PHE programs have better results than ‘stand alone’ health or ‘stand alone’ environment projects? Are there tangible results of the "value-added" by using a two- or three-sector integrated approach?” The documents in this section offer data on various aspects of the added benefits of integrated programs in answer to these questions.

One frequently cited example of the "value added" from PHE programs is the increased participation by either males or females in non-traditional activities. Some PHE programs have increased male participation in family planning (FP)/reproductive health (RH) decision-making. This is a significant change for cultures where males traditionally do not play a visible leadership role in FP/RH and women often have little or no involvement in natural resources management decisions. This section contains documents with a gender theme.

Often referred to as the "first generation" of PHE projects, Integrated Conservation and Development Projects (ICDPs) were promoted in the late 1980s and 1990s as an emerging approach to increase community involvement in conservation. Many conservation organizations incorporated development initiatives into their work in order to meet the needs of communities immediately adjacent to parks and protected areas in developing countries such as Madagascar. While the results of these projects were mixed, many of the lessons learned that emerged informed the current generation of integrated health and conservation projects.

The United Nations predicts world population will grow from 6.7 billion in 2007 to 9.2 billion by 2050 (medium projection). Most of that growth will occur in developing countries. In remote, rural areas of high biodiversity, unmet need for family planning leads to large family size, which in turn places unsustainable pressure on natural resources to provide food and livelihoods. Documents in this section contain analyses and projections of population changes.