Biodiversity persistence in human-modified landscapes is crucial for conservation and maintaining ecosystem services. Studies of biodiversity in landscapes where humans live, work, and extract resources could support defensible policy-making to manage land use. Yet, research should cover relevant regions, and biases in study topics should not lead to gaps in the evidence base. We systematically reviewed the literature of biogeography in human-modified landscapes published in eight eminent biogeography, conservation, and ecology journals to assess geographical bias among biomes and geopolitical regions and taxonomic bias among species groups. We compared research output per biome to the area, biome type, species richness, proportion of transformed land, and the ratio of transformed to protected land. We also compared research output per geopolitical region to area, the proportion of transformed land, the ratio of transformed to protected land, and human population density. Research output was distributed unequally among biomes, geopolitical regions, and species groups. Biome type was a clear factor in research bias, and forest biomes were the subject of 87% of papers, while species richness was not generally associated with bias. Conservation in human-modified landscapes is most important in regions with low protected area coverage, high land conversion, and high pressure from human populations, yet the distribution of published papers did not generally reflect these threats. Seventy-five percent of studies focused on the Americas and Europe, while Africa and Asia were critically understudied. Taxonomically, plants and invertebrates were the most studied groups; however, research output was not correlated with species richness per group. Protected areas alone will not conserve biodiversity in the long term. Thus, a strong biogeographical evidence base is required to support policies for biodiversity maintenance on human-modified land. Under-studied regions and species groups deserve further research to elucidate what, where, and how biodiversity persists in human-modified landscapes to inform conservation policy and enhance efficacy.